Diplo's are super tanky. Everyone doesnt realize this is now the BEST bullet tank in the game. When heath is low, sprint out with no problem. Unlike the bronto, the Diplo is very fast. While passive taming, realize that first feeding you have about 15 minutes until next feeding. Then all quick after that.
Good tanks for raids! Use as a frontline attack in front of Brontos or Gigas etc, can push tames back when attacking so you can use this for defence too. Their high speed allows you to run from turrets when on low health. Worth it when passive tamed as the low kib needed means you can tame more.
Not really useful tame, but they don't do any damage unless they push you off a cliff. Their attacks are all pushing, no damage. Awesome giant walking prime meat machines to kill and harvest when you are taming something useful. Or tame one and name it the Magic School Bus and drive you and your entire tribe off a cliff into the Volcano.
They are probably the best pack animal in the game, for its size and carry weight it moves super fast allowing it to quickly transport huge quantities of supplies over long distances. It's recommended to pair it up with some other animals as guards as it can't do much in a fight and even though it has a massive health pool it regens health pretty slowly.