I did this back at the end of December with these results (copying and pasting a prior post that, for whatever reason, never made it to this forum):
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Post from 12/28/10:
At 17% spell hit (but all from spirit) 4 full duration FoN on a 85++ Raider's Training Dummy, yielded 162 hits, 39 glancings, and 3 crits. 0 misses at 0% melee hit (at least that Recount recorded). Interesting to say the least. Beginning to wonder if they are using our spell hit -- it doesn't seem to be a pet recording issue with Recount -- I sic my lvl 82 hunter pet on the same dummy and it records misses at the expected 2.5% rate I would expect based on that hunter's hit rating.
Next, I dropped some pieces of gear off to get spell hit down to 7% and recorded my first treant miss . . . dropped down to 0% spell hit and got 2 more misses on a single treant drop . . . getting comical. I'd love to be able to pull these guys up in WoL and see if they are missing at all currently -- over 500k damage now on a raiding dummy without a single miss when at 17% spell hit.
Finally, found a way to get to them reliably in WoL. Very low miss rate -- many bosses not a single miss. Highest I found on one boss was 3 misses X average hit of ~1,500 = 4,500 dmg over 4:12 fight = ~18 dps difference. That was the worst case scenario. Clearly the zero miss attempts of 0 dps difference are the best case.
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Since then, I've made most of my reforges to Hit instead of Spirit to see if I could reduce Treant misses to nil in raid content (no reason not to as the Spirit isn't buying me anything). I'm at currently just over 17% spell hit and just over 7% melee hit right now. Recent WoL reports for T11 content show me averaging about .1% Treant miss rate (true misses, not talking dodges, parries, etc.). Back when I had no melee hit, I was around 1.5% true Treant miss rate.
Late December WoL (all hit through Spirit, no melee hit) 23 misses on 1562 swings:
World of Logs - Real Time Raid Analysis
Recent WoL (17% spell hit and 7.19% melee hit) 2 misses on 1613 swings:
World of Logs - Real Time Raid Analysis
There's a definite positive effect with stacking melee hit - it's just that Treants don't seem to be following normal rules. All in all, given the low amount of misses, and the relative dps gain of reducing those misses, going out of our way to stack Hit is probably not a good strategy.
That said, there are some easy things we can do to up our melee hit rate that are pretty much neutral impact other than increasing our Treant accuracy. The main thing is use Hit where you would otherwise use Spi: things like gemming Veiled Demonseye instead of Purified, using a Hit Cogstone instead of a Spirit cogstone, reforging to Hit instead of Spirit when we are trying to up our spell hit rating, and reforging Spi gear to Hit when there is no better reforge on that gear are all things we can do that don't have any negative effect (unless our gear does double-duty resto spec) and yet reduce treant misses.
Is it worth the trouble for the smallish positive impact? Up to preference I guess but I see no reason not to make those sorts of changes. Definitely don't sacrifice useful throughput stats just to get Hit rating, but I don't see any reason not to do 1:1 Spi>Hit conversion / trade-offs -- again unless you use this gear for Resto as well.