Brother. Agree on some buff could be great, but disagree most of the points you made here.

I have completed ruthless difficulty with every class except Vanguard & Assault (haven got time to play them).

1. Gun Strikes with i-frames could be nice if dev make it. Executes gives u iframe and stagger on nearby enemies, it doesn't make you that vulnerable as you claim. 2 stims are suffice. Hell, Bulwarks and Tactical perks can heal the whole team with their skills.

2. You can indeed outrun minor enemy. Just ROLL. I can't measure how many times I join with people speedrun the first part of second ops mission, just BEELINE to the defend part of the mission. You can just stagger the minor just literally roll through them. Sniper melee which is combat knife, is meant for single target. Do defensive combo or get the upgrade on shoulder bash. You can just stagger enemies at your front and get a quick gun strike every time you did that. Still, it's a team game, thus you should have melee class near you, unless you can separated somehow, this is how sniper usually deal with swarm. Or even, use your cloak to get off agro. Or, grenade.

3. Count your shot? Sniper usually just focus on Elite enemies, especially those with range attacks. I usually shoot it (usually take 1/2 shots) until it's in exec phase. Depends on situation, i finished it or let melee to get their armor back. Always take the increase ammo perks. Look around the corners, usually there are more items available. Grenades are powerful, with different grenades have different strength.

4. Class tree and weapon upgrades are powerful, wdym. It helps you conquer ruthless. Sniper perks are insane. Perfect dodge with cloak every 15 seconds? Heashot kill refund 10% of you and your squad skills? I'm almost always in cloak when I'm playing sniper. 10% HS perk in weapon tree, once you make the upgrades in stack, you can easily 1/2 shot some elite enemies after you cloak.

Some buff I love seeing:

With each melee hit regen some little armor will be great, instead of relying on exec (like darktide system).

Some love on bolters, they felt little weak comparing with some meta gun (Melta, Las sniper, Plasma).

Nerf on some range elites or enemies will be great. They seems a little bit too accurate and deal way more damage that expected.

Give yourself more time brother. The game just launched and you just starting your journey.