Looking at your team you have about 13 damage a Turn assuming everyone gets 1 shot off.
Thats enough to take out the tank, position 2 and almost position 3.
You then loose the healer on the earthquake assuming no one falls under 2 hp
Then you win from there fairly easy. I would be surprised if you had another full turn.
I'm new myself but sometimes its best to pick something that goes together really well over worrying about the specific rules. At least thats what I've noticed at the lower silver level.
I think you picked it well in this case. Play by ear on these comps as you might find people countering your magic comp.
I've seen plenty of people play multiple tanks, gelatinus cubes and scavange ability cards as well as they can increase and sort of sustain as other cards die off.
Love that water team great work.

Cenira