If you worry about single target threat generation i'd pick up all talents helping you with this like 2/2 reckoning instead of 2/2 hallowed ground only easing your aoe threat. And tell your co-tank to don't be a dickhead and give you the required 2, 3 seconds to build up enough vengeance to compete.
1) we start with unforging all your stuff
2) enabling raidbuffs (mastery food, stamina flask)
3) reforging into mastery when it's not already on the item (offensive before avoidance even if it's way lower rating)
-> 108.26% with fully stacked spine trinket and <1% dodge/parry off @ 44% avoidance and 220k hitpoints
If you swap that trinket for a 397 stam one, adjust that 4.5% dodge/parry off (relic, boots, chest, waist, wrist: reforging parry into dodge until again only ~1% off) you'll end up with 12 expertise (with glyph), still above ctc (105%), 3.5% less avoidance and additional 12k hitpoints. You have the luxury to adjust your gems (all blue = 75 stam, all yellow = mastery/stam, red = mastery/parry) and
even start replacing single gem items (shoulder, cloak, hands) with full stamina, ignoring socket boni and still end up being at the ctc cap with another 5k hitpoints buffer.
In total: -4% avoidance and less threat for +19k hitpoints, 210k unbuffed.
If you want to keep your expertise high this will eat into either your avoidance and/or your hitpoints and i really can't recommend it. You didn't even step into hardmode progression (yet) thus things like enrage timer couldn't have bother you at any given time.