I still have a fair bit of trouble with Act-3 and I'm forced to kite most stuff and gotta be really careful not to get swarmed.
But as long as I watch my position and play smart my LoH with the relatively high IAS keeps me up quite well.
Though almost all elite packs are pretty much hit'n'run and go in every 20 seconds with blind+serenity to do the damage
I dont use Keen Eye for Deadly Reach but the 18% dmg increase rune. It's better to stack more damage since the armor increase wont enable you to actually tank the elites, so its better to just stack the damage. Just get enough base mitigation not to get literally instagibbed. You're *almost* there mitigation wise, though.
Long story short: You cannot actually TANK anything in Act3/4 apart from normal mobs, and even those are a bit troublesome. Get a bit more mitigation to up your surv a bit and then get more damage. Or well, with really really good gear I guess you could tank some weak elites with affixes that arent super-anti-melee.