I am definitely against nerfing Necropolis and Dungeon.
Increasing the timer – a maximum of 30 seconds per day, okay.
If we are looking for a way to balance the castles within this tournament, Georg's idea looks quite interesting – a fixed cooldown for certain castle pairings, for example:
Necropolis - Inferno, Stronghold, Swamp -/+3k
Dungeon - Inferno, Stronghold, Swamp -/+2k
and consider a few more cooldowns...