Since niches are, in fact, completely made up outside of the level of content they were designed for...anyone can use any weapon they choose so long as it is designed for the content which they will be facing. It is safe to say that due to the weapon's level, and raw stats, it was designed for current content. Thats about as far as this "niche" thing goes in FFXIV. SE gives you a bunch of weapons released with content, you choose which to use for what. He chooses to use his GC lance, and he is making a good choice because that lance was designed for current content. Again, it doesnt need to be the best in any one category to be relevant or useful. The point is that it is viable, and it definitely is. No party will fail current content because they were using all GC weapons...with the exception of maybe Garuda. And that is an honest maybe, since Garuda is actually a gear check in a lot of ways, and requires not just viable gear, but superior gear. Still, I could very well be possible to succeed even with all GC weapons. Other than that one possible exception, I fail to see the problem with his gear choice...other than the fact that it doesn't fit into your min/max belief system. Different strokes for different folks, let him be.