I have a level 75 guy who has yet to do any DLC, or even the civil war!
He has pretty well done everything else though (except the Dark Brotherhood).
There's a solid ~600 hours to be spent in the default, vanilla game. 
Anyway, not wishing to do either of those things - it's time for DLC!
I have to now become a vampire, I s'pose... since I have already played through for the Dawnguard.
I pvssyd with a guy who is on Solstheim @ level 14, LoL, heheh...
He was having terrible difficulties.
I don't recommend that; instead (like the Fallouts etc.) I introduce the DLCs one by one, in the order they were released.
And only once everything else is fait accompli !