Even if you used 10 Pride weapons, it wouldn't screw you over. I wouldn't recommend it if you run 2+ healers, but the bare minimum that you'd have is still 100% Assault. And that's plenty.I run 2 Pride weapons in my Water grid as well, and honestly? I can't even even tell the difference between a full HP Hime and a 50% Hime. I mean, I know that the full HP one is 114% and half-HP one is 134%, but that's hardly a difference you'll notice in a single turn.
If it's swingy for you, then you're at a point where your grid is still low, no? I don't see how that'd be an issue for you. If your grid suddenly jumps from like 50% to 70% because of a boss AoE Overdrive, isn't that a huge bonus you should be happy about...?Defender weapons give you a huge buffer, which is just outright amazing. I have 30% HP in my Thunder grid, and when combined with 20% HP Eidolon, it's just... well, outright amazing. Sadly, not something I can afford to do unless I have elemental advantage. But even when I need to run double elemental Eidolons, the 30% HP buffer does some amazing work.
That said, I'd advice against heavily investing in HP weapons. Dual-skill weapons are becoming more and more common, and will provide you with all HP you'll need, along with the essential damage output. So focus on dual-skills and Assaults(/Prides).