oblits; i'd start them on-table. they have a great selection of weapon options that you can use to fill-in any gaps or else take down that one annoying target!
deep striking them simply means you have that many fewer turns, but it does get their shorter ranged weapons such as the twin-linked plasma guns into range right away...
termies; the only time i'd deep strike termies is if they have heavy flamers... otherwise, they simply make a solid center for force. your opponent will hammer them yes, but while he/she is so focused on your termies, the vast majority of your force is being left to their own devices!
abbadon; dear sweet chosen's teeth don't deep strike him!!! (well, unless you feel like gambling and think you can get that unit of termies to come down with him!)
abbadon is going to attract insane amounts of attention - he needs a unit to hide in... doesn't matter if you stick him with a big unit of chaos marines or a unit of termies - just put him with his buddies!!!
cheers!