I can think of a handful, but it might be helpful to know what you have already played aside from just the Neverwinter sequel.
Mind you not all of these have a keep, but in my personal opinion are definitely worthwhile RPGs.
Fallout series
The Witcher series
S.T.A.L.K.E.R.
Elder Scrolls series
Divinity series
Fable series
Mass Effect series
Gothic series (though admittedly, I own Arcania, but have never had an opportunity to crack it open... which I have heard is probably for the better).
Knights of The Old Republic series
Bio Shock series
Borderlands series
Drakensang series
Dragon Age series
Jade Empire
Two Worlds series
And, although this is another I have never played, I have heard decent reviews about the Sacred series.
ARCANIA IS NOT GOTHIC!
lol
Back to OP :P
Dragon Age Inquisition "so far" may have a castle building and upgrading system for battles online.
Not sure if Forsaken Fortress ever get off the ground, it was on kickstarter last year and featured RPG elements with base building.
Obviously XCOM games are RPG elements and base building :P
Cortex Command
Conquest of Elysium an old style Might and Magic type.
Majesty games.
I can think of a handful, but it might be helpful to know what you have already played aside from just the Neverwinter sequel.
Mind you not all of these have a keep, but in my personal opinion are definitely worthwhile RPGs.
Fallout series
The Witcher series
S.T.A.L.K.E.R.
Elder Scrolls series
Divinity series
Fable series
Mass Effect series
Gothic series (though admittedly, I own Arcania, but have never had an opportunity to crack it open... which I have heard is probably for the better).
Knights of The Old Republic series
Bio Shock series
Borderlands series
Drakensang series
Dragon Age series
Jade Empire
Two Worlds series
And, although this is another I have never played, I have heard decent reviews about the Sacred series.
ARCANIA IS NOT GOTHIC!
lol
Back to OP :P
Dragon Age Inquisition "so far" may have a castle building and upgrading system for battles online.
Not sure if Forsaken Fortress ever get off the ground, it was on kickstarter last year and featured RPG elements with base building.
Obviously XCOM games are RPG elements and base building :P
Cortex Command
Conquest of Elysium an old style Might and Magic type.
Majesty games.
I know that Arcania is technically not Gothic, but it is widely accepted as Gothic 4. Steam even sells it as part of their Gothic bundle (mind you it is the Arcania+Gothic bundle).
Regardless, I would agree that XCOM has significant RPG elements, and it is a great series.
I was not impressed with the Majesty games, but they are primarily RTS any way.
@OP
If you haven't yet, check out this site... they focus primarily on RPGs and I am certain you can find some great suggestions that we are all leaving out: Link