Allosaurus are found in packs and often mate-boosted. Any mate-boosted creature only takes 70% of the normal damage and therefore requires around 43% more damage and torpor to either kill or knock down. The alpha, which for the reason of being the highest leveled is the most sought after, has another bonus on top of this that when together with the mate boost makes them around 2 times as resistant to damage and the torpor it may come with.
Now stop crying about how it takes more resources to take one down and use your time to devise a plan to separate the Allo you want from the rest.
TIP: You are unlikely to outrun one on foot or with most carnivore mounts, so be sure to bring something fast or beefy.
When single taming be at least level 52. Tame a Tapijara. Find a group of allosaurus. Next break one off from the pack by attacking one and leading it away. The others might follow that’s okay. Lead them to a cliff and fly over the cliff. Switch seats and begin to tranq the one you want. When you knock it out lead the others away. Go back to the unconscious Dino and begin to place meat in. Have at least ten Narco per level. The other allosaurus will almost always come back. I suggest taming two at a time. Knock out a second one. Then kill the rest as they might attack your brand new allos....... keep in mind that prime meat speeds it up by 70 percent than raw meat so go and kill some Dino’s. Good luck and happy taming! Also they might kill your new tapijara so make sure you have at least 50 percent health when going close. They killed mine.... but I had three more. Always have a backup flyers.