Preface - this is completely my opinion based on my using Megalosuchus and how she’s evolved in my lineup strategy wise. Also, that’s probably because I have not had the opportunity to level her very much yet.
So the best two uses I’ve found for Megalosuchus are as an opener as an alternative to a tank to feel out the opponent instead of committing something stronger to the field, or as a closer when you need to swap in your last dino. Personally, I really don’t like using her as an opener…she’s just too vulnerable to getting killed quickly. While she will usually still do decent damage, I don’t feel its the best application for her.
Generally, she’s something of a niche dino for me in the arena…I usually try to save her to be a closer if I can. Yes, Megalosuchus always has lower attack than Gorgosuchus, but the trade comes in the counter attack. Especially towards the end of a tight battle, people seem to completely forget she has that, which has pulled the battle in my favor on more than a few occasions. That, combined with most people seem to pull out tankier dinos as the match goes on, the shield can help out a heck of a lot for survival.
That being said, I do find her to be a rather niche dino, than something that I regularly employ early and/or often. She does have a lot of downfalls…like I wish they’d switch out Critical Impact for Defense Shattering Rampage. That alone would change her usefulness dramatically I think. But…as much of a niche dino as she is, those particular situations she really does shine.