Since the added with I24 resist to the IO sets, you can get some extra resist just with building your normal melee/def sets that
are not to shabby. With both the +def epic shields it should not be really a problem to reach +45% def to s/l on top of permanent domination.
As an example, this is how my fire/dark looks (one outside buff from Tielekku)
https://imgur.com/a/Xvo7JFi
if you throw the T4 barrier on it you could even add an extra +5% def/res . with the -to hit from dark and from the interface I would rank my dominator as stronger then my scrapper and stalker. It seems a bit, hm silly from my pov that somebody would not pickup the melee powers. As an example I did run a mission with my bio scrapper that has thrown only psi mobs at my face, not something I like with it if you play at /x4 - /x8 . for my dominator even it has the same bad psi resist the this is not really a issue with perma domination and our good control side.
I would add anohter point to the OP list. If you are not playing a Villian as Dominator you miss something really cool, points to the Villain Alignment Power.....