DirkGently said:
Avoid them at first. Wait until you've got a nice collection of .32 ammo or 5.56, and at first, try to pick your fights. Fighting off a regular Super Mutant is one thing, doing or three is something else. You'll probably end up using a mag for your hunting rifle or two depending on your stats. I typically play the Lucky Perceptive Sniper, able to hit from far away and get a critical hit often. A combat shotgun can do some good, but I tend to avoid using it due to it's deterioration rate.
EDIT: missed the beginning of your post. I'm not familiar with them on Hard, but I'm sure you'll do fine with two followers.
Yeah, Clover and Jericho act as my 'armor' since I refuse to wear it(Bar the merc outfits and leather). They soak up a good amount of damage, whilst I flank and engage those who they aren't fighting. I use mostly my hunting rifle against the 'muties', going mainly for headshots. I have around 70 rounds, which I think should be enough for hard mode against muties.
Are there any huge tactic changes in the harder modes? I sneak around alot, and try to get sneak criticals. I run and gun with sparce use of VATS, in urban areas and use stealth in metro tunnels and buildings.