As a matter of fact I raid 10m as well (we're progressing on Sha right now though, so a few months behind.) From what I can tell, dps checks are roughly comparable and usually more lenient in 10m (10m sha kills are done by the waves of 7 in p2, 25m first kills easily reach second wave of 8 and sometimes first wave of 9). But yes, lets not turn this into a 10 vs 25m debate, and concentrate on the fact that you're advocating haste for dps?? Haste is not a dps gain, or rather, it really only adds to autoattack yet you end up doing lower special damage. 3x Tiger palm > 2x jab + blackout kick.
As for chi, I'm sure someone somewhere did a calculation that power strikes and ascension both result in higher chi/min than chi brew. While I don't disagree, I believe they ignored the fence post issue where with chi brew you straight off start the fight with 4 more initially. Here's a handy chart I made:
Notice that even at the 7 minute mark, chi brew yields more chi (and most of the time by multiple chi) than either of the other two talents.
Only until (roughly) the 12 minute mark does power strikes actually catch up. I am saying:
Sum of (t=0 to 700) [Extra chi from chi brew - extra chi from power strikes] = 0.
Anytime before that, chi brew is still ahead.
I didn't bother to do the math for ascension since power strikes is better in every way but convenience and aoe, but I'd assume you'd need around a 16 minute fight at 5k haste to reach the same extra chi values.
As the vast majority of the encounters in this tier are sub-12-minutes, I keep chi brew for them and swap to ascension for Sha.