Blaine leaped to Kurt's aid after ten minutes of knowing him. Ordinarily this would be a Marty Stu trait, but it's revealed he didn't even consider the possibility that Kurt wouldn't tell the truth—if Kurt had been someone else, or even if he'd met Blaine before he stopped being a Manipulative Bastard, things could have gotten ugly. And they did.
The destruction of Blaine's Relationship Sue status reaches a new level of Tear Jerker when you realize that outside of the Warblers, Kurt and Greg are the only two people who genuinely care about him and are physically there to show it.
Both in- and out-universe: if Finn's locked in Kurt's car trunk, then what happened to Kurt?
According to The Castle, Kurt is fine. But Blaine may be doing even worse than he already was, seeing as hiding in an abandoned hotel isn't exactly following the "get lots of rest and keep things quiet" advice for concussions.
More horror is invoked in-universe at the end of The Curse, where it's suggested that Alex may have sexually assaulted Blaine at some point.
Considering how close-knit the Warblers are and how low Blaine's self-esteem is, it's not hard to think that they give Blaine a lot of solos in-canon because they think he's intentionally passing them up. Or they just want to make him feel better.