If you have a large amount of HP from weapon skills, sure it'll increase your chances of survival, but if you're rarely or never going below a certain amount, then that is wasted potential that could have been extra damage.

Like say if my units had 7~8k HP cause I had several HP skill weapons but none pretty much ever go below 2k HP. That there is a loss of damage.

The only time I would recommend HP skill weapons is if you're still fresh to the game and can't reach the HP threshold needed to survive an event because of lack of time to farm for break limits/low level kamihimes or if you have no other weapon for your soul/to fill other slots.