Deepstrike although not used often can be useful when going second, as it lets the reserved units get their shots in first. In 6th deepstrike is also a lot more forgiving, you only roll for dangerous terrain when landing in terrain (rather than misshap) and the misshap table only has a 1/6 chance of outright killing you. Combine this with 3+ reserve rolls and it makes deesptrike a lot more appealing than it was in 5th edition.
The only things I consider deepstriking are Hellions, Scourges,Ravagers, Void Ravens and Razorwings.
Hellions because they are fragile and have a good shooting attack. You can deepstrike them into some cover (With the baron the terrain tests won't be a problem) as you get to use that 5+ armour save against it. As long as you land near a weekend enemy unit that you can finish off with the hellions splinter pods and earn a pain token your hellions should be in a strong position.
Scourges they can either function like the hellions: deesptriking and earning a pain token on the turn they come in. Or as traditional seepstrike suicide metla, even with blasters deepstrike can get you a shot on side/rear armour.
Ravagers, deepstrike is useful when you are going second with no night fight, sometimes there is too much firepower on the board and you decide to reserve your ravager in order to protect it. Deepstrike lets it come on in a better position on the flank (than if you moved in from the board edge) and still shoot which can give you shots on side armour!
Voidraven/razorwing, lets you get behind enemy flyers, come in in a better position.
Hope that helps.
EDIT: The Duke does not let you assault after deepstriking.