This isn't a problem with fluid aura being insignificant, this is a problem with people not realising how powerful it actually was back in HW/ARR. Stormblood removed it's damage entirely leaving it as just a tool on those occasions when a pack had a single stray that wasn't playing ball.
I assume you knew the importance of keeping Assize on cooldown rather than saving it as a healing cooldown from fairly early on I'd guess? You realise that on a single target, Fluid Aura did as much DPS as assize? And back in ARR/HW it was actually even more powerful relative to our nukes? 150 potency every 30 seconds for 0 MP, back in a time when our main nuke was 170 or 210 potency and we were always having to conserve resources.
It contributed plenty, just people slept on it because A) DPS just wasn't anything like as important as it is now and B) Min maxing DPS wasn't as well understood either. Some players were too bad/lazy to use it considerately or even get in range at all thus a lot of people expected the worst when they heard it's noise.
Regarding the EX4 (I assume this is Barb right?) fight, honestly I think it's a bit of a smoke and mirrors encounter and whilst I do think it's the best primal we've had this expansion by a good margin, I still don't think it's a classic. It doesn't space it's AoE bursts out as conveniently as EX5, but they also don't hit anything like as hard, people only really need to be watched if they have vuln stacks, otherwise it's still not that threatening unless you're in an under geared group.
Ironically EX5's key AoE+ movement mechanics hit significantly harder I think? If they were a little more frequent or the puzzle phase was shorter it'd be a far better fight for it. Without Lilybell and a stock of Raptures to handle it, it'd be much more intensive.
Regarding Eye, you know it could proc off AoEs right? Including it in your spreadlo changed things up with it.