They aren't good.
However, there may be a way to make them "work"
First of all, this is for Iron Clad Dreadnoughts. Sorry if you had your heart set on another type of dread, but that is what this strategy calls for. Well that OR a Relic Leviathan Dreadnought from FW. (rules here from FW) Works with that too.
Note, the "Relic of Darkness" rule states: " A model with this special rule may not benefit from any rules or bonuses usually conferred by being part of a particular Chapter, detachment or formation."
BUT Kantor's rule and the Honour Guard are not conveying their bonuses in such a manner (chapter tactics, detachment or fomation bonus) and as such he can still benefit from them.
So first of all you have to take Pedro Kantor. So if you DON'T want Imp Fists Chapter Tactics, once more, sorry. I know this keeps getting more and more restrictive, but this is for people who want DREADS above all.
Now go back and look at your Iron Clads. With 4 A base and 2 x CCW, they get 6 Attacks on the charge, now 8 so long as they are withing 12" of Kantor and his Honour Guard. If you want to use your specialist weapon rules, you still get 7 Attacks! Leviathans are much the same way! Alternatively you could use some contemptors, though you are sacrificing some attacks and armour for shooting, though they do have their shield.
But what about delivery you ask? Why yes, delivery. Well first of all Ironclads are 13 Front 13 Side Armour. Leviathans are 13/13/12! AND HAS A SHIELD! So that can really help. BUT the answer is Lucius Drop Pods, which give the dreads Shrouded the turn they arrive.
How can you make that work even better?
1- Locator Beacons- Available on Storm Ravens and Scout Bikers
2- Inquisitor Servo Skulls
3- Drop Pod Assault - make sure all your dreads come in TOGETHER, set them up back to back, or back to back to back, to prevent shots on rear armour.
HQ- Pedro Kantor
Elites- Honour Guard(5): Co Champ, 3 x HG w/ Power Sword, 1 x HG w/ Power Axe, Standard of the Emperor Ascendant
Elites- Ironclad Dreadnought: Lucius Drop Pod, Seismic Hammer, Storm Bolter, Meltagun
Elites- Ironclad Dreadnought: Lucius Drop Pod, Chainfist. Meltagun, Storm Bolter
Troops- Tactical Squad (5)- Grav-gun, Sarge w/ Combi-grav, Drop Pod
Troops- Tactical Squad (5)- Grav-gun, Sarge w/ Combi-grav, Drop Pod
Troops- Scout Squad (6)- 5 x Sniper Rifles, Heavy Bolter, Camo Cloaks
Fast Attack- Drop Pod
Fast Attack- Scout Bikes (3)- Locator Beacon, 1 x Astartes Grenade Launcher
Heavy Support- Relic Leviathan Dreadnought: 2 x Siege Claw w/ Melta-gun, Lucius Drop Pod
Heavy Support- Centurion Devastator Squad: Omni-scope, 2 x Grav Cannon w/ Grav Amp & Hurricane Bolters, 1 x TL Lascannon & Missile Launcher
Heavy Support- Storm Raven Gunship: TL Assault Cannons, TL Multi-Meltas, Locator Beacon
You use your scout bikers infiltrate ability to position well for a Locator Beacon first turn deployment of your 3 dreadnoughts. You can easily block LoS for your Scout Bikers with these BIG drop pods and big dreads. Then keep those bikers alive at least until you bring your Storm Raven in loaded with Kantor and the Honour Guard. What is really nice is that it is an assault vehicle for your power weapon wielding, fearless, preferred enemy (ork) +2A, 6 Attacks on the charge Honour Guard PLUS Kantor and a Company Champion!
Then you have 2 locator beacons on the table for the rest of your drop pods. Hopefully, you can get your tac squads last for some late game objective grabs.
Sniper Scouts are for objective camping. Heavy Bolter is to make best use of the Imp Fists doctrine (and I had exactly 8 points left).
Cent Devs are really good for Imperial Fists. With tank hunters, they can do some damage, and the omni-scope allows you to split fire and have the Lascannon/Missile Launcher guy blow up vehicles while the other two use their Grav-Cannons and Hurricane bolters (which ALSO benefit from Imp Fist doctrine) kill off infantry.
And since you are Imp Fists, NEVER FORGET ALL YOUR DROP PODS HAVE STORM BOLTERS. 12 additional shots