Both Cade and Hammer Station's bonus bosses' aoe could be avoided if you stay far enough or stay behind the box. Especially the Sith in Cade.
The fact that you CAN does not mean that you're supposed to. IE: I know a spot where you can solo Gil without taking ANY damage at all. Does it means that's how you're supposed to do it? nope. A guildy takes upon himself to solo everything he can. The other day he was soloing Lucky (and succeeding). He soloed at least one of the Ilum WBs during the gree event, and so on and so on.
He is melee btw so if you want to argue about workarounds to boss mechanics you might as well introduce every single possible glitch, losing and kiting technique available in the game.
Fact stands: 3 of 4 bosses are designed to hit the whole group, with minor exceptions.
I'm also fairly sure that you are still in melee range of Gil if you position yourself carefully.