Can anyone confirm whether the Easy/Normal/Hard/Very Hard are working as intended?

I'm playing on Normal (Red Helmet) but my marines are dropping like flies...

Shooting at CSM's tend to be easy enough, i can drop them with a few bolter rounds, but whenever i get caught out by Frag Grenades or enemy Bolter fire, i'm dropping just as easily.

Just been watching a chap on YT doing the Hero difficulty and he just waltzes through the missions with no issues at all, even though shooting bolters at CSM's takes forever and enemy grenades barely tickle his units.


So i'm just wondering why, on Normal, Frags/Bolters are ripping my blueberries apart :/

I can do that - having played it from "Veteran" to "Mighty Hero" - and insure you that it always worked as intended. It's important to note that, as stated in its manual, the game was designed to be played in that "Normal" (Veteran) mode, so it's quite balanced that way. Which means that, indeed, as soon as you're in range to kill CSMs with a couple of bolter shots - though, yes, it can take a while sometimes -, they do the same... Playing safe, maintaining good lines of fire, using cover or blind grenades (on yourself, which usually forces the IA to waste all its action points moving closer to your position), advancing in an orderly manner while some of your troops maintain overwatch, and being always on the lookout for opportunities to tip the (firepower) balance in your favor - anything (a piece of wall, a croutched position after walking instead of running, a weapon with a longer range or accuracy bonus at the right distance, etc.) which can help you land a few more shots than the enemy, meaning (if they're concentrated on the same targets) a few more kills than them, will definitely transform an hard-looking game into the kind of walk in the park you've witnessed on YT. If you're regularly taking grenade fire, you're not cautious enough for example, since the 9 (range) squares of those require your opponents to push quite close to your guys before any shower can begin. This can't be prevented at all times - in tunnels for example - but shouldn't happen a lot usually... It's (really) just a question of method, though RNG can still bite you in the rear from time to time (but far less than in the old X-COM titles for example).
That "normal" mode is the main dish of the game - "Hero" just adding a few bells & whistles to enforce stricter gameplay (and more epic battles !) -, so you should expect it to be reasonably challenging if you're new to the game. Just keep at it and you'll improve in no time :). Otherwise, remember that there's (absolutely) no shame in starting first with the "Space Marine" (easy) level... Games are meant to be fun !