Alright.. the skyhammer is.. not ok. Not really. The devastators are generally workable with grav cannons but you are paying for the 2 assault squads just to get a first round non snap shot with other weapons besides grav cannons. Grav cannons are salvo 3/5. You can do the same thing with just 2 devastators squads. You can even split the devastators, put half into dedicated rhinos and the other half into drop pods that you get from the command squads. The command squads you can put onto bikes and still pay for a drop pod so you don't waste your fast attack slots. Mixing in BA gives the ability to get fast predators/vindicators for more speed.
For the psykers look at telepathy for psychic shriek/shrouding/invisibility. If the psykers are on bikes instead of rhinos they can cast the invis/shroud.
The secret with iron hands is to mix in a sanguineous priest from the BA to give your IH a 4+ feel no pain. You can also use a command squad with an apothecary to give the 4+ FNP as well. With both of those choices you can put people onto bikes which gives one of the best all round maneuver capability.
If you are coming in with drop pods, it really needs to be overwhelming. One of the advantages of the skyhammer is you can bring pods in first turn w/o them being in your count, but unless you bring 2 skyhammers in and a command squad pod on first turn it's kind of like leaving them out to dry because the devastators can't really move.
The dread is ok in a pod. you get a mover/shooter and if you can plant the pod onto an objective then your opponent has to make a choice.
Really figure out as many ways to gain Ignore Cover for the devastators, auspexes on the librarians or maybe use Ravenguard librarians so one of them can take Hunter's Eye for the squad ignores cover.