The lack of haste on our tier set is actually not as big of a problem as it initially looks. Consider that we will probably be using:
Belt of Arctic Life, 40 haste
Greater Speed cloak enchant, 23 haste
Bracers of the Broodmother, 36 haste
Ironmender, 36 haste
Evoker's Charm, 42 haste
T8 hat, 59 haste (54 for 10-man)
T8 shoulders, 48 haste (44 for 10-man)
One or two rings with 30+ haste each

This adds up to just over 300 haste already. The target for softcapped raidbuffed haste (that is, a 1.0 GCD with Wrath of Air and Imp Moonkin or Swift Ret Aura) is 359. So switching a single crit-itemized tier piece for one with similar stats but haste should get you close to this soft-cap.

For now, I'm doing leather only. I think it's fair to assume most guilds, your clothies will get to roll on the cloth drops long before we do. Once the full list is up for resto/boom, we'll probably add some of the better cloth gear.

I wouldn't go so far as that. If you tend to use RG in bursts or have short periods of burst healing with Nourish then provided you have Nature's Grace critical strike isn't that bad as it somewhat equates into "bonus haste". Naturally it isn't as 'good' as it used to be when NG lasted 15 seconds but if you adapt your usage around the new version you still get some acceptable results.

Wouldn't go as far as what? Is there any stat you would prefer to have crit over?
Crit will never ever be worth it unless it will have some effect on hots.

Isn't this the case where the stats are pushing the playstyle rather than the playstyle pushing the stats? I'm currently at 575 haste and use CF to push it even higher. Even so 60-80% of my healing in general case comes from HoTs. No matter how you look at this, there is no way I can effectively convert all my haste into healing numbers so most if it is typically going to waste, however, I don't feel like taking crit would help me in any sort of way (since so much healing comes from HoTs anyway and this haste at least lets me not worry about having or not having a totem, boomkin, whatever else so at least I feel like it's doing something for me.

Seems to me that crit is a primarily tank-healing stat - it lets you achieve higher raw HPS at the cost of less mana, and it synergizes with tank-healing talents like Living Seed (ok, that's pretty much it I guess). If you talk about raid healing, crit seems to make no difference at all. If you cast direct heal at someone in the raid, usually they took damage, they are not in the danger of immediate death and the job is to get them out of 10-20% HP zone to 50%+ HP zone and let them top off from HoTs before the next "whack'emall" boss ability.

However, if you had sufficient crit you could go for a bit different play style and rely on crit to generally top off people in the raid with one cast and no need for HoT - pally style. However, I don't think we can push crit high enough for this to be a viable healing strategy, and the only spell that we could use for that would be a glyphed healing touch and it doesn't seem to mesh that well with the resto talents that we have.

Crit is obviously not useless (like say strength!) but it is really quite bad. Not only is haste better for 'burst healing' than crit, but it also helps with rapid decurses (which come up on Yogg), and its throughput increase has low variance, unlike crit. It's not even clear to me crit gets more living seeds per unit time than an equivalent amount of haste.

I have shed most of my crit except in obvious best in slot pieces (like the Malygos quest neck) or tier pieces, which obviously we would all wear regardless of what stat they had because the bonus is so good.

Hots will crit one day. Unfortunately Blizzard feels resto is in a good spot right now, and doesn't want to rock the balance boat with a large change.

You're missing a major problem. Going over 450~500(not sure of exact number) haste will take your Nourish cast with Nature's Grace effect under a 1 second cast when fully buffed. This is detrimental because it means we can't queue our next Nourish cast, we have to wait for GCD and then cast another. So spamming/chaining it at every 1.02 (my current cast time) seconds during huge tank damage phases will be that much slower, not faster.

So yes, we have a haste soft-cap, but I think of haste as filling up a glass of water. You fill it up to the point that you're thirsty to (soft-cap) then anything extra is just bonus, until you start spilling water because it's going over the sides(hard-cap?). I'm not totally sure if crit is worth going for over haste at this point, I'm still trying to figure that out myself. Anyone got any clues I'm missing?

You 'should' only be using Regrowth if you are getting the benefit of both components of the heal else you use Rejuvenation or Nourish/HT*. Even that comes into question once you have 4T8 though but until more people start actually getting that it's hard to know for sure especially in hard modes where you are required to maximize your healing as much as possible - it could not be enough still.

This change should be a nerf of around 1,500 mana to most well geared trees however we can now give whoever needs it 15,732 mana which is a welcome change.

Also stuff just got a bit one-sided in the mana regen from intellect or spirit department. This is with replenishment set at 80% uptime.

Intellect:

Spirit ->	1000	1100	1200	1300	1400	1500	1600	1700	1800	1900	2000
Intellect
1000	47.22	48.65	50.07	51.49	52.92	54.34	55.77	57.19	58.61	60.04	61.46
1100	46.56	47.92	49.28	50.63	51.99	53.35	54.71	56.06	57.42	58.78	60.14
1200	45.98	47.28	48.58	49.88	51.18	52.48	53.78	55.08	56.38	57.68	58.98
1300	45.47	46.72	47.97	49.22	50.47	51.72	52.97	54.22	55.46	56.71	57.96
1400	45.02	46.22	47.43	48.63	49.83	51.04	52.24	53.44	54.65	55.85	57.05
1500	44.61	45.77	46.94	48.10	49.26	50.43	51.59	52.75	53.91	55.08	56.24
1600	44.24	45.37	46.49	47.62	48.75	49.87	51.00	52.12	53.25	54.37	55.50
1700	43.91	45.00	46.09	47.18	48.28	49.37	50.46	51.55	52.64	53.74	54.83
1800	43.60	44.66	45.72	46.78	47.84	48.91	49.97	51.03	52.09	53.15	54.21
1900	43.32	44.35	45.38	46.42	47.45	48.48	49.51	50.55	51.58	52.61	53.65
2000	43.06	44.06	45.07	46.08	47.08	48.09	49.10	50.10	51.11	52.12	53.12

Spirit:

Spirit ->	1000	1100	1200	1300	1400	1500	1600	1700	1800	1900	2000
Intellect
1000	32.75	32.75	32.75	32.75	32.75	32.75	32.75	32.75	32.75	32.75	32.75
1100	34.35	34.35	34.35	34.35	34.35	34.35	34.35	34.35	34.35	34.35	34.35
1200	35.88	35.88	35.88	35.88	35.88	35.88	35.88	35.88	35.88	35.88	35.88
1300	37.35	37.35	37.35	37.35	37.35	37.35	37.35	37.35	37.35	37.35	37.35
1400	38.76	38.76	38.76	38.76	38.76	38.76	38.76	38.76	38.76	38.76	38.76
1500	40.12	40.12	40.12	40.12	40.12	40.12	40.12	40.12	40.12	40.12	40.12
1600	41.43	41.43	41.43	41.43	41.43	41.43	41.43	41.43	41.43	41.43	41.43
1700	42.71	42.71	42.71	42.71	42.71	42.71	42.71	42.71	42.71	42.71	42.71
1800	43.94	43.94	43.94	43.94	43.94	43.94	43.94	43.94	43.94	43.94	43.94
1900	45.15	45.15	45.15	45.15	45.15	45.15	45.15	45.15	45.15	45.15	45.15
2000	46.32	46.32	46.32	46.32	46.32	46.32	46.32	46.32	46.32	46.32	46.32

So any thoughts on the mechanic of 4pT8?

4pT8 doesn't take Gift of Nature, Improved Rejuvenation and Genesis into account. This results in 25% healing loss, compared to if it would just do a instant rejuv.

Yes, one could say that this isn't a hot and thus no hot bonus (Empowered Rejuv seems to work though) and it's not a spell and thus no spell bonus, but if you look at mechanics of other sets/glyphs/bonuses - they all work the way common sense suggests them to work - with full potential.
Glyph of Rejuvenation, for example, isn't a spell either, yet it benefits from GoN.

I was really hoping it was a bug and Blizzard would fix it in the next patch, but.. not a word from them.

The way RJ works: (338+SP*0.376*1.2)*1.04*1.06*1.3 - [please note the coefficient might be very slightly off]
The former part (in brackets) is the actual spell itself and the parts outside of the bracket are the talent modifications we gain to our healing done.

Empowered Rejuvenation is within the brackets (the *1.2) so is part of the base spell which is why it (by your assumption here) works for the set bonus while those outside do not.

Once I get the 4 part bonus myself I can test it and confirm what does and does not work.