So I stumbled upon this quest very early on my NV experience and decided to put it off until I was stronger and better equipped.

Now I'm at level 22 with some decent armor -- Mark II Combat Armor -- and weapons; this led me to believe I could handle the Super Mutants. Instead, I got dominated. There are just too many of them.

Are there any specific weapons I should use, or maybe a perk that would help out?

The Purifier perk will increase the damage you do against Super Mutants, but only for Melee and Unarmed weapons. You armour should be alright, what weapons are you using?

nope they pretty much [censored] your butt the best i could do is use my silenced sniper rifle till they saw me then used the high explosive missiles to finish them off it took a try or two but i got it did oh also i snuck all the way up the mountain with no detection and had the good super mutant help me on the way down another time i tried.

I mainly use the 10mm submachine gun, hunting rifle, and Ranger Sequoia/.44 Magnum. Some explosives, too, but my explosive rating isn't very high. My character isn't strong enough to carry any of the super-heavy weapons.

Some fire resistance aids might help. If you're ranged weapons, keeping your distance and sniping helps too. If all else fails take a well equipped companion with you.

Maybe my game's Very Hard difficulty really is bugged...they always fall fairly easily to my sniper, modded cowboy repeater, or carbine. The first time I killed one I was like, 'that was it?' :/

Well supposedly they nerfed the sniper rifle in a one player game which is just [censored] [censored]. Because seriously it's a one player [censored] game why do you need to nerf something, it's not like WoW were you are competeing against other people were it actually makes sense to nerf stuff...

ANYWAYS... sorry about that little rant, but seriously go pick up the sniper rifle man, and get the silencer for it. Sneak your way up and blast those [censored]es and if it shows "caution" just hide behind a rock or something so they can't find you till it turns "hidden" again. Then repeat, and you should be good to go. The sweat thing is you won't even get touched.

The Ranger Sequoia should be good enough, but I'm basing that on statistics since I haven't used it before myself. You might want to try getting a Marksman Carbine (or the All-American). The Gun Runners sell Marksman Carbines. They are quite decent at medium/long ranges, and the All-American is one of my favourite weapons for Guns.

Do you have any companions? They could make quite a big difference in combat, depending on which companion you have.

The super mutants seem to have relatively high DT, which means low-DAM weapons like the 10mm SMG are going to be useless against them, and explosives aren't really your best bet either. EDIT to add: The Sequoia is high-DAM enough to be useful here, but you will be using a LOT of ammo in this area, and that gun's ammo is harder to come by.

Approaching with a guns character, I've had good luck using:

• A hunting shotgun loaded with slugs, with the Shotgun Surgeon perk
  
• A suppressed sniper rifle
  
• And, in a pinch, dousing them from a distance, aiming outside VATS, with one of the mutants' own Incinerators (despite having a lousy Energy Weapons score)

Good luck! Let us know what eventually works for you.

Where can I find the sniper rifle? Do you recall who sells the silencer?

The Gun Runners or the Arms Merchant at the 188 Trading Post may have both for sale.

You can also find a free-to-take sniper rifle (in poor condition tho) on top of a bunk in the Recon's tent in the CampMcCarran front outer yard. Well, you could pre-patch. I haven't checked to see if it's still there.

if you have that floating robot, you will be able to target using vats the nightskins when they are using stealth boys, also have another sidekick. and if you can have, an ncr trooper with you. i like using the light machine on them when i have high gun skill. go slow up. that way you will only have one or two t deal with at a time.

Lily with a Super Sledge really helps at black mountain. She can keep the melee Nightkin (what really messes me up) busy while you come in from the side with something high powered.

Indeed. There is also a free-to-take Sniper Rifle hidden in a bombed-out building (full of traps!) outside North Vegas. The fallout wikia likely has more info.

Boone and the gauss rifle seem to make it manageable.

When any one weapon can be enough to carry you through the whole game, even if it is a single player game, it needs a fix.

Single player games have balance too.