Not every character needs to be front and center and have a story constantly to be a great character or even stand out amongst the others.
He is a soldier for Vic and the group and that strikes me as having a lot of character to the extent of extreme loyalty. He's always involved in the story indirectly but just not as in your face as some of the others.

Yeah, he barely even speaks in the first five seasons.
But that builds up his image as the dutiful, unquestioning soldier, which adds to the poignancy of the ending.

LOL @ OP. I actually said something very similar to my wife when he first grew his beard. That was definitely his high point in the first 5, maybe 6 seasons.

That's part of the reason he's my favorite Strike Team member. Not bogged down with the melodrama in his life. Season 6 and 7 are really when he steps into his own as a character. We see he's a competent leader and sadly, is being led down the same road as Vic.
You are sin.