I do enjoy the antag system. I don't really try hard as antag though, and instead just make myself a sort of mini-boss to be dealt with here and there occasionally. It's fun to actually play it like the bastard that shows up to be a problem, not a team-wiper, and still get rewards out of it. However, it definitely has it's issues.
IF YOU LOOK AT NOTHING ELSE, DEVS, LOOK AT THIS:
MENTOR MATCHES/BELOW LEVEL 10 MATCHES NEED TO BE IMMUNE TO ANTAGONIST INVASION. FOR F*CK'S SAKE THESE NEWBS CAN'T EVEN PUT THEMSELVES IN THE ANTAG POSITION!
FIX THE LEVEL/MMR SPREAD BETWEEN WHAT MISSIONS ANTAGS ARE ALLOWED TO INVADE- DO NOT LET THEM INVADE MORE THAN 50 LEVELS 20% APART. FOR F*CK'S SAKE, LET THESE BEHEMOTHS FIGHT EACH OTHER INSTEAD OF THE LEVEL 5'S, YOU'RE PUTTING CHIHUAHUAS AGAINST GODZILLA
My first problem with the Antagonist system is the fact it can land in the lap of newbies that have absolutely no idea what the heck is going on, and no gear to deal with it. I mean that in the strict sense- I'm in a mentor match, and the level 1's-9's suddenly see "level 292 antagonist has invaded your mission!"? They cannot even interact with the antagonist system themselves until level 10, and may not even be informed of it until then. How is this in any way fair to the new player, OR the teammates playing with the new guy? What if it's a non-mentor team full of sub-10's against this guy?
The game is hard enough in most cases, and trying to get friends to play more of it past lvl 8 or 9 is like pulling teeth. Tossing an antagonist several hundred levels higher into a game, with late-game characters, stats, and fully upgraded rare weapons that have lethal abilities... It's throwing newbies against the wall like waterballoons full of blood. I can easily see people going "THIS is what the game is like? To hell with it."
That leads me to the other main problem I have, is the level/MMR spread of antag/raider pairings. Most antags I've seen vastly outlevel basically anyone else I've ever seen playing- most, that is. This means the same problems as listed above befall the other people playing- the game god decides to pair you with someone that's got free selection in an arsenal of characters, skills, and weapons, vs. you at level 50, whom doesn't even have half what the game could offer because of the gold and blueprint grind. The best games I've had with antagonists is when they're largely even playing field. That accounts for 2 of the antag games I've had. Every one of the others went one of three ways:
1) The antag was lowbie and had bad enough stats they were like fighting a mook, sometimes easier because of the MMR difficulty stuff
2) The antag one shots entire groups of people with things like Loaht's cluster grenades, and annihilates the team before second mission phase (any mission).
3) We had a level 200+ on our team that had absolutely devastating firepower which wiped out the antag instantly every time.
There was one outlier with a lvl 300+ Harec. Guys aim was *insane.*
Still, the gear grind/level advantage is absolutely a real thing, and it's the main reason the antagonist system is an eyeroll mechanic at this point.