well 60 sage in general is really tough. But yeah I suppose you could get decent damage reduction. 10% from mastery, -18% from staff shielding, -15% from 60 set. so that's 43%- then with a CS pot you could hit -58% And when appropriate you could go ape for another -20% which would be -78%. I imagine that would be the way to go and switch between the 60 staff and sleep staff mostly. Also with elder of rites and the entire set on perservering that would be -90% crit damage sustained which would help a lot against the 50 bow, 50 shield, and 60 2hand sword.
It would still definitely be tricky but going ape and sleep staff, keeping your 60 relic proc'd (easy since everyone is trying to kill you) and your tick healers going once they're asleep you might have a chance to get close enough to them to root them and get a couple shots with the 60 staff to kill them before needing to go ape/sleep again. If against a bunch of people not much you can do but with an ok team and having a static -58% dmg -90% crit damage you might just be beefy enough to kill some people.
OMG that actually sounds nice.
Just to add, you'll mainly be switching between Bird, Ape and human.
Unfortunate that bird form has no AoE's tho :S you'll have to sacrifice bird form M Crit for when you need to AoE (and in 60 arena everyone is way too close to not want to AoE).
Maybe go for 70 mystic-mage instead tho? You get 3x from 65 set AND 3x darts.
probably better to use dual hammers in 60 arena. Make use of stun while it still works.
5k+ M attack, Mcrit maybe 60+ (buffed), 150 M Crit dmg (10+8+8+8+8+8+18+24+48+10)
Note: Kuso+5*Amplyfying+Staff Spec 3+relic+staff
+Vanguard of the Anceints for Capped Magical Crit dmg!