Best Raise Spectre build? Best monster for Spectre?

correct, hatred does not work with flame sentinels.

The tentacle miscreations that are always available have a lower level wich is noticable.
they cover a smaller area with their attack and dont fire as often as flame sentinels.

i like tentacle miscreation too. I played a while with them in a sire of shards staff and GMP gem.
they fire in an 180° angle and thanks to GMP hit reliable at long distance. Without gmp the gap between each projectile gets too big (imho).