Aliens will always be the best of the series...
The predators use the aliens as the ultimate biological weapon. That means that they have a losen control over them and they know how to contain them. This experienced predator certainly had a previous encounter with them. He may have studied their anatomy, their strengths and weaknesses. The alien tongue may penetrate armor using strong muscles and sharp teeth, but i cant see no reason for an agile, buffed up, predator wouldnt be able to rip it off,
predator trainees have done the same in AVP 1, the very host of the predalien IIRC
Its a film and exaggerations are expected, but we have to have to note a few things. The aliens can adapt to every situation and use any host to create a superior killing machine, based on the host's very own characteristics, so that the prey would have no hope to survive. The average alien grunt is no match for any human, but the toughest predators can stand a chance against inferior material of aliens.
These aliens were created from weak enemies, like humans, dogs and other forest animals,
normally those animals couldnt threaten a predator in hand to hand combat, at any circumstances, but as alien-human hybrids, they present a moderate threat. On the other hand the predalien hybrid, is expertized on killing predators, now thats a real threat for every predator, even for the most powerful, agile, skilled and best equipped ones.
If the aliens were to invade the predator world, they would be much more powerful, using a mass army of predaliens,
that way, the aliens efficiency as a species remain untouched IMO.
They just stretched the strengths of the predators a bit more than the usual, as the film has a predator as the main character.
The self sacrifice of the predator was a heroic achievement, similar to a skilled Masai warrior killing a lion and similar to the one Swarzeneger has done, against the first predator.
If a normal guy like you and me had to the face a lion, (unarmed without any kind of gun) we wouldnt make it (most certainly)
aliens based on human DNA are for the hunter predator, as much of a threat, as is a wild dog for the Masai warrior (the one skilled enough to kill a lion with milli weapons),
those wild dogs/alien-man hybrids can be tough at packs, for the Masai/predator to face,
but he can beat them one by one, with mili weapons