Anyone ever purchase above level 1 in tower regen/damage? How about ANY Deathpenalty? More than one rank of Income? How about these idea possibilites for Citadel Upgrades:
The Deathpenalty upgrade also reduces the XP/Gold the enemy team gets from killing you and anyone on your team (-5% each? -10% each?). Nice to have if you've got AI or New Players on your team, and semi-counter if your behind in deaths/kills.
The XP bonus upgrade begins to give you gold, instead of XP, when you reach level 20. It's not useless the higher level your DG becomes now. Good strat to invest in if it looks like a long game.
The Grunt Damage/Armor upgrade also increases the rate that grunts appear/spawn, and/or, the number appearing (Attack could increase rate of spawning, Defence could increase #s) and/or how fast they move. I'm aware war-score increases some of these already. The increase in Defence/Armor should be greater also. Damage/Spawn Rate to Counter enemy teams that ignore AoE damage, or Defence Upgrade to counter AoE DGs who you don't want eating your grunts for easy snacks.
Tower upgrades reduced in price and/or increase the bonus both give; if you spend 4 levels of gold upgrades on towers, it would be nice if enemy demigods had to change strategies, builds, items, or at least raise their eyebrows when they see such solid/deadly towers (that you spent thousands on). Counter to enemy teams that ignore Tower destroying powers/builds/tactics.
The second and above levels of the Income Upgrade also reduces the cost of Artifact Items? (-5% per?) or for all items.
Just some ideas that might make the citadel upgrades more strategic and desireable.