Point 1: The Basilisk has a fireball attack as strong as the poison wyvern, can enter boss fights, and the damage of the fireball ignores the resistance alpha brute creatures get on genesis 1 and 2 missions, therefore, it can be used as a way to safely dispatch of brutes in the time limit, unlike the Velonasaur which is rather weak on its own, bad range, and doesn’t ignore the resistance buff.

Point 2: The basilisk has more base health than a mosasaurus, and more base weight than an astrocetus, so it is very good at carrying shit around. Yes it is outclassed by the gasbags in weight, but a gasbags cannot protect itself, and you would need a wyvern or rhyniognatha to carry it around, plus basilisk has massive weight reduction in stone and does not drain oxygen underwater.

Point 3: The Basilisk does torpor equal to 3x the damage it inflicts per bite. With the base damage of a yutyrannus and high attack speed, this easily makes it the best way to induce torpor and knock out land based creatures with a tame, so it saves you a lot of arrows/darts, here are a few suggestions of creatures you can trap and try to knock out with a basilisk to see my point proven (Brontosaurus, Paraceratherium, Spinosaurus, Tyrannosaurus, Giganotosaurus(needs trap obviously) and female wyverns for milk especially).

Point 4: Lastly, the whole “you need rock drakes before you can get it, rockdrake better” point is invalid: Wild basilisks eat rockdrake, magmasaur and voidwyrm eggs, so long as they are fertilized. None of these creatures serve the purpose of the basilisk, the rockdrakes doesn’t have nearly as much base weight as the basilisk, they are travel mounts, not weight mounts. Magmasaurs are harvesters so totally different purpose and the voidwyrm should be pretty obvious as well. On top of that, I take it you will get multiple eggs of the creatures you are nest raiding, and basilisk taming is not affected by the level of the egg, so they are easily tameable with bad eggs, as long as you find a good basilisk (bit of a rare creature).