There's a flipside to this, and it's what Djay and I talked about after the game with me. He spent 140k to get that Yhetee (or whatever Yhetees cost, they're about the same as Rat Ogres), and that is a significant expenditure. Now he is in the situation where his Yhetee is MNG - and will be replaced with a journeyman lineman. That's a huge TV and strength change caused by one injury. He's really lucky that the 2 deaths came on other players and not on the Yhetee, or he'd be pretty much fucked for good. Yes, you get 5 str, yes you get MB or Claw, but you're putting essentially 3 players worth of TV and cash into him. There's a large reward there, but it's also very high risk, especially with the AV 8 big guys (Rat, Yhetee, Mino). The AV 9 ones are more durable, and Trolls are more durable yet, but I won't include a Troll in my roster until I have 12 stable players, and enough cash to buy a Black Orc or Blitzer should one die.
The thing to remember is that the big guys are all balanced around your team being the same with them as without them. In that case, and with how wildly unpredictable the game is, I feel it's better to err on the side of caution and not get bent over early on should you take a bad injury or death on your big guy (which, if you're playing good players, is going to happen the second they hit the dirt).
It's great that you're having good success with him, but as he gets more powerful, you'll start seeing people saying "You know...this team would be a lot easier to deal with if I just fouled that guy out..." And AV 8 isn't that hard to do that to.