Varric and Sten aren't exactly traditionally attractive. Some people might like them, but some people like Aveline.
And Vega is as far away from the standard model of attractive as Aveline is, really. Dude's as close to being a Krogan as you can be and still be human. It's just men seem to have a broader definition of attractive. And FemShep can sleep with him in the latest DLC, even if he's not a romance.
And Sebastian is an LI, even if you can't sleep with him.
Really If you've got about 8 party members, and you want to have a choice of LIs for both genders, then once you've excluded the siblings, golems, dogs, robots and other obvious non-LIs, if you're fairly attractive you're probably going to be drafted for LI duty, whichever gender you are.
Though ME did get away quite successfully with offering the ladies a horrible spiky monster. If they hadn't Vega probably would have been an LI.