They will never nerf water teams. Rumors say that they will be strengthened in the future (as well as the other mains) so stop asking for it. It's never going to happen. They will however become less dominant when stronger ninjas are released.

As for OP, there are 2 hard counters to Lightning Blitz. Han and masked man.

Han with a Sage naruto and support from behind can do a lot of damage and will effectively remove all but Iruka's and the barrier's buff. You can add a kage ninja to have a barrier of your own or use roshi if you have him. If you have lower initiative odds are you will loose unless you are using immortal teams.

Masked man will immobilze LM for 1 turn and remove his buffs, then you can take your time turn 2 and kill him. Again initiative is important here too.

The tenten lineup is a gamble since if they kill either your tenten or your mei (depending on your setup) on move 1, then you loose.

It's less important than in Han's case since you will stop LM turn 1.

But if they have guy and mifune for example, turn 2 you will need a faster move 1 than them, otherwise mifune will use his mystery and LM will recover from the damage you did turn 1. Even worse if the manage to kill your damage dealer with such a move. In the end theone with the initiative will have the largest advantage in the fight.