I think Prometheans can actually be fun, but their design just needs some fundamental changes.
Their weapons are not fun to contend with.
The homing projectiles have got to go. The needier is fine because needles are slow and easy to dodge. But the corner-bending property's of the surpressor and the bolt shot leave so much to be desired. Not only do they lack originality but they essentially make everyone on the battlefield an aim bot.
The H4 bolt shot was actually a good weapon, tarnished by annoying enemy behavior in the campaign and by the idiocy of 1HK starting weapons in MP.
The suppressor would be cool if it lost the homing properties, but had a much larger clip. That way it could be used as a support weapon, surpressing enemies behind cover.
soldiers shouldn't be analogous to spartans
I feel like Soliders were a bad attempt to extend the EliteSpartan dynamic to the new faction. That explains health and survival behaviors 343 programmed them with. But as HP only, enemies, they don't fit.
Make them more akin to Jackals/Marines. Like Jackal Shields, they should have a clear color coding system to relay to the player their remaining health, and they really shouldn't have much HP. Offset the reduced health by increasing situational awareness and/or numbers.
Also make their hit reactions more satisfying
Teleport should be nothing more than a dodge animation, not a mode of transportation.
If a promethean does teleport, the player should be able to predict where they will materialize and pre-emptively attack, just as you can with Covenant enemies who dodge.
They also shouldn't be invincible while teleporting. Perhaps hitting them while they are teleport would do more damage, or insta-kill.
even tank enemies should have satisfyingly exploitable weaknesses
This goes for H2-5 Hunters as much as it does Knights. Bullet Sponges are much more fun, if skilled play/resourcefulness allows you to circumvent those sponge properties altogether. The Knight weak spots make for a better engagement, but it leads to rather one demensional strats for taking them out. CE Hunters were cool, because with the right footwork, and the right weapon you make short work of them. It was a dynamic that encouraged getting up close and personal and handsomely rewarded the risk. Now, we are encouraged to keep a healthy distance and deal a bunch of damage over time.
fuck crawlers
Seriously, fuck those guys. Maybe it wouldn't be so bad if they weren't using H5 bolt shots and surpressors. But i dunno.