Finally finished the game.
A couple of things I would like:
1) Be able to play the unlocked tracks in the game, not just in the fortress. I am not a big fan of the "farting music" that both 4 and 5 have and it is a real shame I can't blast Quad Machine during the campaign or any of the other good tracks which are there.
2) Chainsaw to replenish all ammo. The fact that you need to chainsaw one guy, wait 30 seconds and chainsaw another to get back to full ammo (which is still incredibly low) is just annoying.
3) Mech gameplay, for obvious reasons (Titanfall).
4) More powerups through out the game, I found only one berserker pack in the whole game, there might have been more but I never found them and I did run through the entire arenas most of the time. 3 quad damages I think, 2 speed boosts. Mega Spheres, however, did start appearing quite regularly during the later levels.
5) Monster infighting would be great.
6) Fists to do damage.
Things I liked:
1) Damage masks on enemies.
2) Higher mobility (movement speed is still low though and I don't think there is bunny hopping in the game, I could never trigger it).
3) More "video game" oriented map design makes encounters and exploration much more fun.
4) The option to look like the OG DOOMguy
(took it the first moment I could and never even entertained the idea of taking any other suit).
5) Combat flow is, for the most part, fun.
Things I didn't like:
1) The first two missions are just meh, just like the last two. The game should have ended in the Tower of Babel, that was a very nice location.
2) We missed all the fun of the initial Hell invasion.
3) The story telling. The antagonists are all the same in most video games today it seems, constantly shouting "but you are the baddie, we are the victims here boo hoo, why are you so mean, waaaah" SHUT UP! Vega and Hayden are both castrated like nothing balls "you can't shoot at Mars, waaaah!" just shut up! Just terrible. I actually enjoyed the story in 4 a TON more than here, it is probably the only thing I did enjoy about 4. Story here is just trash, nothing more to add to that really.
4) Marauder is the biggest combat flow killer of all times. Whenever he appeared in any fight the whole encounter just ground to a halt with his insta-shield and green eyes nonsense, good grief, what a terrible, terrible, TERRIBLE enemy design. Good thing there are only a few fights he appears in. The other bosses are about a million times less annoying, only the Marauder is a complete buzz kill.
5) Unmaker is pure trash though, can only inflict a fraction of the damage in 30 shots what the BFG can do in 1, literally a USELESS GUN!
Summary:
The difficulty itself was pretty ok, I played on Hurt me Plenty and I think it was about right, the enemies still killed me in like two hits the few times when I got him, luckily the dash and double jump with the air control rune allowed me to dodge about 95% of all attacks so I ended up with over 30 extra lives at the end. I'm not sure what the higher difficulties add beside enemy HP because the damage the enemies inflict is extreme even on Hurt me Plenty, the moment I stopped for any reason all my armor was instantly gone and HP dropped to around 20. I have this feeling, and I had it in 4 too, that the more HP you have the more damage the enemies inflict. I got full armor and HP (150/200) and took a hit or two and all of a sudden I am down to like 20 HP and the next hit I take drops me to 11 HP, the next to 6 and then the next kills me, it is really weird. The slayer gates were pretty easy, there were plenty of normal encounters which were much more difficult. The game is pretty decent, definitely better than 4 but I wouldn't put it above 3, maybe on the same level as 3, both have things the other does better. 3 has better story, atmosphere, environments, Hell and overall feel, 5 has better gunplay, gore and movement.