Yep. I made a post regarding this in another thread recently. Here's a list of perfectly good Horus subs that can be obtained without REM. There's a good range of color coverage for Horus and most of these creatures are good in a variety of teams.
Echidna (Farmable in many dungeons)
Blue/Green golems (Farmable in a number of dungeons)
Hera (Can be obtained from Hera Descended, this is probably the easiest of the descends, sort of a prerequisite for later dungeons since she has Gravity)
Siegfried (Can be obtained from Heroes Descended, fairly easy if you're prepared)
Cu Chulainn (Can be obtained from Heroes Descended, fairly easy if you're prepared)
Valkyrie (Can be obtained from The Goddess Descended, this dungeon is very tough)
Hera-Is (Can be obtained from Hera-Is Descended, this dungeon is very tough)
The only issue is that some of these dungeons these monsters are in are frickin' hard, but if you put forward the effort you will eventually get an acceptable Horus team regardless of what you roll in the REM. It's just that at first you will need to use specialized teams to get a few of them to start building your Horus team.