I would not bother coating the impeller housing with epoxy. The two problem areas are the inlet and over tightening the screws. A hose clamp will keep the inlet from cracking. Using plumber’s goop or silicone to enhance the O-ring seal and going easy with the screwdriver will take care of any potential leaks.
With these simple precautions, I have used Danners inline with no problems. The local koi shop has lots of Danner inline installations, again with no problems. Note they don't seal the pump with silicone goop or use a hose clamp on the inlet. Not being overclockers, my guess is they have fewer tendencies to over tighten fittings.