I think IP has a decent proc rate?
Yes, Land Demolisher in tandem with his basic combo extensions provide decent proc rates indeed. The fact that he will almosst always be left behind on party plays can be quite discouraging though.

Plague-centered gimmicks only really shine in Henir. Enemies on any other environment either possess too much resistances or die to easily. The closest thing to a healing tank the op is looking for is Blade Master.