he means the the skill breakthroughs on the main characters. In china the mains can now get breakthroughs were the mains have 2 kinds of elements in their kit for instance water main also has lightinging element and some of her skills fuse with that element and on of those skill is shark bomb which becomes more op that it was :P

for her to go back doing her job as an healer right now you would need the following modifications:

1) Healing Jutsu (the standard attack) should grant, after the healing, immunity to any debuff it just healed for 2 rounds (so if she heals a target poisoned and immobilized, that target should get immunity to poison and immobile for 2 rounds, but would still be free to be chaosed, ignited, blinded, etc...)

2) Regenerative Healing Jutsu should not only heal but also eventually resurrect dead people, bringing them to as many hp as the mystery heals the other targets while also granting to them (the resurrected people), for 1 round, a 100% boost to def and res and if the mystery gets interrupted she should get for that round two additional standard attacks.

3) Water Clone, when on the field, should take the first controlling debuff directed to her in her place or should eventually get healing jutsu as standard attack, in the place of the water whip, if azure fang is controlled.

I honestly think this would be the very minimum for her to work fine as an healer right now, considering the lineups we have.

But if you run monkey king as summon mystery you get it even if you didn't select the clone passive. That said if all the 3 modifications had to come on live selecting again the clone passive would be indeed a good option for her, differently from now (i doubt he meant to propose 3 different modifications, i think he meant to add all the 3 together). i think he just talked about the clone to give again a value to that passive too, since right now is largely outclassed by the other 3.

And no, the main issue right now is not ignition, but the fact you do not heal who is dead (that's why, i suppose, he brought in the fact regenerative healing jutsu should also resurrect).

If you run, lets say, tsunade sannin war, sakura summer and water main with a tank or kushina habanero in move 1 you are left with 2 ninjas in round 2 if you face edo hiruzen or agk teams. Thing that is not true if you run an heavy shielding team (like bee sst, naruto six paths/kurama/six tails, normal gaara, earth main).

If instead water main is alive in round 2 and faster than the enemy shisui/minato hokage, with his suggested modifications both sakura and tsunade get back to life and heal the team back by around 1/2 of the total life, making so the battle go on ul to round 3 at least with the compulsion that you need to kill first water main.