Yeah, the best evasion maneuver is to not get detected in the first place.
After that, I just dive deep and go from there. If the enemy is right on top of me and obviously has a really good fix, I will nail the engines and make a turn at the last second. Always heading away from other escorts, and the convoy if possible. Depending on how far away the other escorts are and whether I'm in the closest one's baffles, I will keep full power for awhile, reducing it to half and finally 2kts. I don't really make depth changes unless it's deeper.
The super-destroyers that are running in "god mode" obviously get around anything you can do. In this case, a save reload is warranted.