Currently I'm having druid with 3/5 revitalise. Should I reroll and try to get berserk? Or just stay with that is good enough for the time being..
Depends on what you're looking for. Revitalize is great for the Arena. Berserk is more all around, it is great for raids and Arena.
I personally have Berserk on my Druid, but Revitalize on almost all my other Heroes except Ninja/TG.
No Revitalize is really strong. 3/5 is good enough to just leave there till the upper rankings in the Arena or possibly forever. It's all about synergy and a 3/5 allows your Heroes to take damage before receiving heal. 3 and 4/5 are the best imho
I've rolled a 5/5 revitalise on my Druid and wish it had been a 3/5 or 4/5. It's a great skill for Arena, although you could say 4/5 would be better. Since an Arena match doesn't last that long you'll love an early heal thanks to your talent.
If however you're all about raids then you'll really want that 5/5 Zerker for 30% less waiting time between heals. Annoyingly my Smurf account has it from a fresh Druid...