Regardless of how it's approached, if the person in question is the unsavory kind, neither approach is going to work out. You either open up with an advice (which can be unsolciited) or ask them why they're doing what they're doing (which is what we have now). It's an offense if people take it as one.
The allagan Museum is still a level sixty dungeon, a post-end game dungeon no less. People by that point should have a general understanding of each skill as they gain it, especially in regards to BLM and DRG whose skills are all steps to their gameplay and each one progressively adds on; Enochian gives a flat damage boost (so there's no reason to not use it at all). If it was a matter of them not knowing how to use it or not using it effectively, it's a different story but I'm not getting that vibe as opposed to "mind your own business its my dps".