And we're saying you get use out of him on Offense, just not on Defense.
But here's the thing: If you put him on Defense, you get 0% use out of him on Offense. There is no GL that you can use on both Offense & Defense in the same TW or the same GAC round. It's always a choice to use your toon in one or the other.
So LV requires you (in your opinion) to put him on Offense. What's the big deal?
As for Starkiller... He requires 2 zetas and 2 omicrons just for himself -- and omicrons are far more scarce than zetas. Top that off with the zetas required by his pre-requisites and you put yourself farther behind than just 6 zetas.
There's no logical argument that Starkiller is a better investment than Vader.
**THAT SAID**, this is supposed to be a game, not a job. If vader subjectively feels like a pain in your patootie rather than something you'd be happy to have, then absolutely skip him: because you're playing the game for fun (or should be).
If you stop playing the game for fun and only play for the most efficient path to power, you're going to tire of it very quickly.
It's just a mobile game: play for fun. Get the toons you're excited to get. Invest time in the game modes that delight you to play. Score those upgrades that put an evil glint in your eye. The rest? Don't worry about it.
Me? These days I play mostly just for the KAM mission. I don't pretend that Maul "isn't worth it" or that it was impossible to grind him out on Conquest. But the way feats were structured, Conquest just wasn't any fun to me. It still annoys me that I can bring in a GL and have ewoks outspeed my GL on **node 1** of Sector 3 and kill one of my toons before I can move. What a pain in the backside. But it is what it is. Some people think the challenge is fun, and more power to them. I get annoyed, so I choose to play something else that is fun.
This is the way.
So don't try to logic your way into the decision to skip Vader (or out of it). Just think, "What sounds more fun?" Then do that.