I got the impression during the two ecaflips I tried, that they really shine at later levels. They kind of need a lot of skillpoints invested to tilt the odds in their favor. In the early game at least earth is all over the place, and water's damage is kind of low.
This is true.
Basically, you need those passive maxed. So before 21 where you can max your "main" passsive skill your damage is kind of meh.
Water is especially lackluster early because you need to cast fleas to stack the damage bonus and with low AP/Range/MP/Skill level it takes a really long time but later on you can be done in two turns and start to shine (the life stealing fleas are great, and the skill that allows you to pounce on foes is awesome damage).
Earth gets its randomness reduced a bit by levelling tarot and the ability to draw another card in case of crippling effects from bad draws. To be fair i never tried an earth eca so i can't really provide good insight on how they work, if it's anything like dofus, its early levels are rough because your main damage ability can also heal the enemy and you don't have the mobility to engage kiting foes.
Fire is okay at lower levels but gets really great when you start stacking some dmg and critical hits. Multi hitting (x3) 200 dmg crits from Die Alright is bound to be spectactular and i did it by level 30.
I'm having tons of fun playing my fire ecaflip right now and i'm still kinda low level (46) so it's all up to taste i guess.