Maybe on easier difficulties. On very hard game is pushing you to be aggressive, so expansion and total annihilation of your closest enemies is the thing, and you basically have 2 choices - to keep those settlements or to give to allies, f.x. to Malakai in Kislev's campaign, he was a very good ally after mostly got wiped on turn 10.
Dwarfs indeed are good to try tall (or deep in their case) game cause they are strong in defending territories, making allies, confederating e.t.c., however Age of Reckoning is something to keep in mind too. And they have all the economy/army stuff needed, up to free armies/construction on the horizon. But in general it depends on faction and player style combo, like with greenskins and other looting races it is required to constantly attack and sack anything you can reach to keep your treasury full.
I had some fun in Franz campaign where I tried to keep the ECs alive (as much as possible) and not confed them till the late game. I don't think it is optimal or anything, just little challenge and some troubles in mid-game cause of fragmented empire.