Completed it on the first try with tactical, heavy with plasma and sniper with las fusil; that combo will make light work of helldrake

Yeah. I'm using Assault class. I know it's by far the worst class in the game but it's so much fun to play. My biggest problem is that I don't do enough range damage but when I get close up for melee the Chaos marines just destroy me by the time I can do enough damage to them.

First try on 2nd day when lethal was fresh with 4.0. The class setup i ran was Heavy (with Plasma), Tactical (with GL of course...) and Bulwark. You really rely on ranged classes and should consider switchting off Assault for that operation or keep trying until you make it.

Cheese it with GL and bulwark who knows how to heal his team

I found GL Tactical, Las Sniper and Bulwark had the most consistent success. GL makes mincemeat of Chaos Majoris and Extremis, Las-Fusil is really good on the bridge, and Bulwark gives much needed sustain and instant revives for those tight situations on the bridge.

I did it as Vanguard. ♥♥♥♥♥♥♥ hate it, worst one for sure, This tomb section with single ammo crate, bridge with fire and specials spawn, boss itself with mini puzzle, misery

It's mostly based on luck with your teammates, i do recommend switching from Assault, very weak class and even weaker at Chaos. Tactical with GL is probably the best choice

1 on ad-clear, and 2 on boss-dps, you can go full ad-clear and there's a loadout checkpoint before the Heldrake area.

a tactical that parry/mark with auspex, a bulwark that have Rinvigoriting Icon as perk and a sniper with Squad Renewal are for me the best composition for lethal. the interaction of Squad Renewal and auspex/banner are amazing. all other perks beside that mentioned are useless.

I beat it with assault before patch 4.1 was released. The team was assault, vanguard, and sniper. Chaos marines are sitting ducks for a sniper. We fed him all the ammo.
Really any class combination will work it just depends on what sort of teammates you end up with. I was lucky on that run they were both pretty decent players and also really good teammates. Everyone did their jobs.

I cannot.
I failed all my tries.
The last Lethal of all.
Assault, Bulwark, Vanguard, Tactical... Zero success.
I am levelling Heavy and Sniper atm.

This one is a tought nut to crack. A good Sniper and a Tactical are a good start. I needed four runs with randoms to complete it. It´s by far the hardest mission on leathal.
But the helmet looks sick...

We made it guys. If any of my fellow Battlebrothers need help with this or other mission, you can add me. I will be more than happy to help you.

Tactical ping is quite helpfull, heavy and sniper are great too.

I got it third try, all tries with randoms.

My first try ended from a bad kelbrute spawn during a massive wave, second try ended at the bridge.

Yeah