I actually like using such terms in character. Soldiers in real life use such terms, calling people Jarheads or Sappers or whatever. Why shouldn't D&D characters use similar terms for things like Paladins and Clerics? Of course, I don't generally use the same terms, but sometimes it's appropriate. I don't use "tank" in character, because that word originates from the method of manufacture for creating those things... a method which would not exist in a fantasy setting. "Meat Shield" however seems fully appropriate. I also have characters with terms like "Boomer" (mage focused on fireballs) or "Bandage" (cleric focused on healing).

JaronK