I was more talking about the possibilty of a missing "elemental weaknesses" aspect, rather than the water thing.
Different FFs showed a different number of elements.
Some games had 4 if I recall? The biggest number being 8.
In a game like FFXIV that has 6 elements (8 if you consider light and dark but I guess these will be going away with 1.20?) it seems a bit unbalanced, or uncoherent, to have such a two-split elemental wheel that doesn't include water.

Of course they could reform the elemental wheel into a single one, with 5 different elements.
For example:
Fire > Ice > Earth > Thunder > Wind > Fire

This doesn't make much sense, it's just an example.
They leave water out of the elemental wheel and make so healing spells are water based.
Uhm... it works I guess.

Altough, maybe it's just me, but personally I don't really like the idea of water-based healing spells and 5 elements wheel.
The 6elements one just sounded all much better to me.