I was cruising with my pair (levels 25 and 42) through that canyon on the west, then suddenly tek rex jumped off the cliff to roar at us. I didn't see his level at first so I was unsure and thought to turn around and run, but decided to stay and fight. I didn't fight him, I ATE HIM IN LITERALLY 3 BITES! It was level 4, didn't even take any damage and my other allo didn't even take part. If it's so, I presume I could take down level 20 to 30 rexes easy with these guys. I have a rec at home, but he's just for showing off, tame allow for business!
If you get a pack of at least 3 good leveled allos you can kill anything except for obviously Titan and giga our tribe has a few with 14k HP and 400 melee and with 3 of them we can easily take out alpha rex and other strong dinos, also they are a lot faster than most carnivores and not to mention the highest level gets an "alpha" boost where it can do the gash attack they do in the wild where they slow you down and make you bleed
The highest level Allosaurus will become an Alpha if at least one other is nearby; you do not need 3 to gain the Alpha Bonus.
The best way I find to breed Allo's is to find a pack with 1 150, kill off the other two and tame a 150 Allo. Do this for 2 150 Allosauruses and you can breed a nasty army of these things. You'll be able to take on Rex's like they're dodo's. Wyverns make for east kills, too. Just watch out for Alpha's.
The only thing a good pack of Allo's cannot take on, is a wild Giga.
Allos have the speed of a carno and the strength of a rex; a well-rounded creature to go for. In packs of three or more, the highest lvl allo will become the alpha (the one with the cheeto dust cloud), which can do bleed damage that deals DOT and slows down a target. Definitely recommend mass-taming for PvP.