I'll outline some of my high grift findings, some info may help you?
I've started playing my wiz again solo and cleared a 50 the other day. Getting to the RG in time is no problem, I usually have 7+ minutes left and then its just a case of l2p issues, dodging the RG attacks etc.
My gear is no were near perfect right now, but with the right rift I think 55+ is doable. The build im using gets stronger as you push the grift levels.
http://eu.battle.net/d3/en/profile/Smudge-2122/hero/58605259
Looking at your build it kind of lacks a bit of focus for 50+, both in gear choice, skill choice and gems. Everything will 1 shot you so you have to really stack damage and fish your way through a rift, skipping mobs that will explode, skipping most packs etc and herding large groups of whites together, to sit in, letting your APD bracer keep you alive whilst you meteor them down.
Notice on my build I don't use any defence gems and even have glass cannon passive. Focus and restraint for extra DPS, no RROG, Skelly shoulders for an extra cheat death, no defensive armor buff, choosing the DPS one for more regen. regen from MW/conduit etc. Astral presence for more regen. 4 APOC on my source.
Regen is key at this level of play, teleport into a big pack of whites, stun them with calamity, hit a meteor, run out, teleport back in, meteor, move on.
Taeguk gem will give you both a DPS boost and armor boost, get one, get it levelled as high as you can and youll see a difference. It's a pain to keep the stacks up but just takes practice. Most of the skills youll be using maintain the stacks so after a bit of practice youll see it sitting a max stacks through the whole rift.
Cheers,
Matt.