With the recent change to swipe (swipe does 50% more threat), I believe that swipe now beats lacerate at all levels of damage given reasonable AP and crit levels. Is that correct?

Here's the math to answer my own question.

Swipe damage: (AP * .063 + 108) * Naturalist bonus * feral instinct bonus * armor penalty * (1 + crit chance) * 4pT6 bonus
lacerate damage: (AP*.01+88)*Naturalist bonus * armor penalty * (1 + crit chance) * 2pt7 bonus
lacerate DOT damage: (AP*.01+64)*stack size * naturalist * mangle * 2pt7 bonus

Swipe DPS: swipe damage /1.5
lacerate DPS: lacerate damage / 1.5
lacerate DOT DPS: lacerate dot damage / 3.0

swipe TPS: swipe DPS * 29/14 * 1.5
lacerate TPS: 29/14*(lacerage damage+1031)/ (2* 1.5)
lacerate DOT TPS: lacerate DOT DPS * 29/14 / 2

Based on a 70% armor reduction from bosses, here are the results:

For AP 4735, crit 30%, no T6 and 2pT7 I get the following:
swipe TPS: 1095.2
lacerate TPS: 786.1
lacerate DOT TPS: 282.5
total lacerate TPS: 1076.045

swipe TPS - lacerate TPS: 307.7

So at least at my level of gear it is better to simply swipe every time and not bother with lacerate. At least I believe; it's harder to model the value of keeping a stack up but losing threat via multiple lacerates compared to multiple swipes. For this it appears that the TPS for lacerate's ticks is not as good as a single swipe relative to a single lacerate, TPS wise. Still, every time you lacerate you lose more TPS than a DOT of lacerate will tick for. That alone makes it pretty significant.

Did you consider the impact of Lacerate on R&T with Maul?

If for nothing else, it'd be worthwhile keeping a stack running.

Mind you, the 4t6 bonus will go right fast if you insist on tanking anything interesting. The health differential is just too big.

Not necessarily. The only thing that R&T needs is a bleed going, not a lacerate. As long as you have another class providing a bleed of some kind lacerate will be suboptimal. Naturally you'll need to do a lacerate if you don't have that.

Your formulas look right, but you're missing some important factors. First of all, this is only comparing Swipe spam against Lacerate spam. Second of all, you're not counting avoided attacks. Additionally, boss armor rates have gone up. If you don't have a warrior sundering (very possible if druid is tanking) it will be as high as 44% armor without or 34% with. The bleed from lacerate is more valuable in all of these cases (assuming you're not letting it fall off ever). As already mentioned, the bleed for RnT needs to be considered if not provided by someone else. Those stats also look quite low and I'm hoping are unbuffed totals.

This does make Swipe spam much closer to Lacerate spam. After factoring in miss rates I think Lacerate spam comes out slightly ahead still. However, just using Lacerate to keep the stack up and Swiping otherwise was already best single target TPS. This change just makes it better.

You're likely right. The DPS for a swipe is 352. The DPS for a lacerate is 72. The DPS for a Lacerate DOT 5-stack is 278. The total DPS for lacerate + DOTs is 351; the total dps for swipe is 352. I think you have to get into a bit harder modeling than I have time for to determine whether keeping the stack up is reasonable for DPS at that time though. According to Rawr you'd lose about 200 DPS which sounds about right, but I'd like to look into it further.

The stats are mine and based on my character with typical Naxx-25 raid buffs. They are low; that is sort of the point. At higher levels of gear you will see swipe greatly overtake lacerate; at 6000 AP and 40% crit, for example, you'll see swipe with almost a 300 TPS advantage. Without an armor debuff, the bonus does favor lacerate again at my gear levels, this is true - but without any armor debuff you'll see a lot of classes suffer greatly, so it's somewhat of a good assumption that it exists. Avoidance doesn't effectively factor into this all that much. The bleed debuff does not cause that much threat relative to the swipe or the lacerate attack directly.

More interesting is that my estimates show Swipe threat can now pass up Faerie Fire threat. That threshold is roughly 6k AP and 40% crit (not too hard with raid buffs) with Sunders up. Without Sunders it would be closer to a 7500 AP and 45% crit region.

I have seen the Polar set useless from the beginning tbh. Stacking stamina like that doesnt seem to do any good.
And stamina is something druid have imho had loads of since day 1 of WOTK.

Right now im running with my tank set in raids and im getting roughly 47k HP, 45-47% dodge, 32k AC with a decent amount of AP to do around 2,5-3k DPS on patchwerk while tanking. I do have to give up Defenders Code for Gossamer for the sake of HP to get these stats but everything else stays the same in my gear, no polar pieces etc.

So i would say stacking that set for stamina seems meaningless, you will get those health numbers with actual tanking gear too

Ah.... just figured out that you must have had 47k AFTER the 25% hp reduction from Sartharions add?
What does that make your raidbuffed stamina before the debuff in this gear?

Vesperon's debuff doesn't change your stamina, so it'll be the same with or without the debuff.
Power of Vesperon

As for health, our current Sartharion MT runs with around 53k raidbuffed hp on this encounter, but that's with sta trinkets and polar gear. I'm pretty sure he switches those out for avoidance/armor on other encounters.

Regarding expertise, how does it equate in PvP? is there a cap like hit rating on a lvl 80?

No you don't, the 45k+ number is before Vesperon's debuff and it doesn't require the polar set, but if people are lacking gear in those few slots the polar set could help. Regardless of that, I really would not ever switch out Defender's Code for Essence of the Gossamer (except the aforementioned Sarth+3), 32k armor is very little (I have 39.5k atm with zero buffs, as reference) and unless you're tanking Sarth+3 the extra few thousand health is worth nothing compared to the armor you lose by not using Defender's code and other armor items.