Kaan

When you spam HS more, hit loses SEP and haste gets better. This is because hit then more or less only affects your offhand, and haste then affects more of your yellow damage (Heroic Strike).

According to your example with the 1,00 speed weapon:

Now take two 1,00 speed weapons for mainhand and offhand - haste speeds both up. In 100 attacks, 1% hit will be one attack more, if I read it right. With 1% haste you will have probably 2 hits more (mainhand and offhand) with this scenario, both can crit, glance, miss, or hit normally. However, 1% haste will clearly be better in most of the times, especially with the usage of HS.

Not without steady incoming damage. Take the worst example, when you have zero incoming damage: your offhand needs to crit all the time with very high damage to deliver enough rage to HS every time AND sustain the standard cycle (BT, WW, Rampage and perhaps sometimes Demoshouts). Of course, your offhand can't crit every time and your offhand won't have so high damage that it gives 12 rage for hs, 30 rage for BT, 25 rage for WW and 20 Rage for Rampage (perhaps 10 rage more for Demo Shout, or even more when Demo Shout resists - and of course every 2 min Battle Shout), because our offhand only does 65% of the damage, the mainhand would do. However, for steady HSing I would prefer a fast offhand because it's simply steadier rage income, and better to plan.

There are fights like Teron, you have sometimes high damage income, and sometimes only little or zero damage income. In this fights you can almost every time press HS. However for HS spamming like the warrior against patchwerk pre-BC with 1550 dps, you need insane buffs and some luck with your offhand, to sustain HS and the standard cycle without any damage income, even with the best equipment available. Note: a warrior equipped best-in-slot with Sunwell gear, only has about 130 to 160 hitrating.