From lvl 2 to lvl 50, you get the full amount of runes - 48 (4x12) for each class in various combinations. From lvl 51 upwards, you get half that amount, rounded down. So, if you are a warrior and get 5 might, 5 spirit and 2 magic runes (12 total), you will get 2/2/1, respectively. 6/4/2 transforms into 3/2/1. The leadership upgrades are also halved. In essence, at lvl 51, you will get the leadership upgrade of lvl 25, for example. So, rather than getting over 1000 leadership upgrade, you will get only 500 as a warrior.
Still, it is a pretty meaningful upgrade, and one can never get enough runes
The dwarf, Trigger is also great - he will upgrade his special skill several times. It will provide up to +25% critical chance to all archers. This is great for everyone who likes archers.
EDIT: BTW, doubling the attack of the female chars is wondrous. It makes them act not like 4000, but like 8000 fairies. Imagine the crit they'll inflict