Guardian is a useful Keystone with an extremely long CD; reduce it by 15 seconds.

30s Guardian is by no means OP, not even in the ballpark, but it makes it more usable. 45s cd when in 5 seconds people do five times the amount of damage the shield provides, well, yeah. Honestly, if I was on the balance team I'd take it down to 25 seconds on the PBE and see how that feels.