Obviously they're in the game to prevent lame strategies, but in fights like SCOB Turn 4, there is already a tough soft enrage (Bahamut's Favor for DET+). If you can handle 4 or 5 stacks, you deserve the chance to continue the fight. The problem with hard enrage is this:

Groups that go for world first are encouraged to split in two. 4 members join group A and 4 members join group B. Those 4 members get all the loot and all the upgrades so that they can beat the enrage sooner. This fucks over 8 people and leaves them with zero gear all for the sake of world first. It also makes world first impossible for people who want to evenly distribute gear in their FCs. It's pretty shitty. No one has a chance to beat the world first group cuz' no one is gonna have 4 pieces of high allagan per person and weapons on 4 people in week 2 except for them.