Although I've played Iron Warriors for a while, it's mostly been at smaller point games so for me I think it's hard to say at this point. My group is building up to larger points, so I'm at least doing a lot of theoretical list building. We know our stratagems favour vehicles, daemon engines, havocs and Cult of Destruction units, so I would lean towards those for us - maybe taking basic troop loadouts and then stacking whichever we buff with Warlord traits. Of them, I think Vindicators look good for their high Toughness and our strat to re-roll the number of hits. Pairing one of them with a unit of Havocs and maybe a Las-Predator for anti-tank could deal with a lot of threats and synergise well with our Warlord traits.
I've tried rolling a Defiler as a distraction unit, and it kind of works - but the problem is that the list needs other heavy hitters to capitalize on the distraction. The games that I've played haven't been big enough to fit them in and in retrospect I loaded it out wrong if it was a distraction, so it's been a bit of a challenge to experiment with.
We know we're getting a new codex with big changes to our unit profiles in the W bump, and seeing how the points shake out will mix that up a lot. But if Havocs stay at T5 and go to 2W that is a nice plus, or rolling 10 man squads with 2 heavy weapons and the warlord trait to ignore movement penalties could be nice.
One strategy I want to try is having a mostly basic detachment with Havoc backup, with a second detachment rolling two Vindicators and a Las-Predator with a Warpsmith and Dark Apostle. The Dark Apostle can make them -1 to be hit, Warpsmith and our strats heal them, we have strats to re-roll wounds on 1, and using the strats to reduce AP and gain a FNP is great for vehicles. Vindicators also benefit for the re-roll to number of shots, although it's limited to just one sadly. I feel like this could survive a lot while pushing out a lot of punishment
Another interesting strategy could be rolling a Terminator Lord and a fair number of Elites, with a second detachment of a Dark Apostle and Oblits and Daemon Engines. Give the Warlord the extra hits stratagem on Cult of Destruction and Demon Engines and move them within the Dark Apostles prayer for -1 to be hit by incoming fire (alternatively, make them Mark of Tzeentch and try to boost their invuln with a Tzeentch Sorcerer). The Terminators can deal with light infantry and maybe heavier infantry depending on their loadout, while the Daemon Engines rip through things at range. Then, when needed, just drop in the Oblits in range of re-rolls and the Warlord Trait, and use Endless Cacophony to blow anything away. It should be tanky and would pack quite a punch.
I'm not sure how we'll these ideas would handle objective secured though, depending on the points value of the game in the end.