Physick is too weak for lvl 60 casters?

[Saggo]

If I recall, Sustain heals the pet at a rate based on the Summoner's HP for a few tics... why it works off the Summoner's HP and not the pet's HP, I don't know but that could be part of the problem.

Sustain does 8% of the pet's HP a tick, and at 10s duration, you'll get about 3 ticks in, for 24% of the pet's HP healed. 24% every 10s is actually pretty slow in this game, especially 50-60.