I usually edit the raws to make dwarven civs naturally tolerate and start in all the biomes that the goblins do - that helps the dwarves not be passed over when the race sorting begins.
Dwarves use the new EXCLUSIVE_START_BIOME tag to start their setting point, but nearby dwarven hillocks can be in most biomes except desert, swamp and tundra, right? (Just peeked at the wiki
. I don't see why they couldn't have [SETTLEMENT_BIOME:FOREST_TAIGA] in there for a start. I also tried tweaking the biome support numbers up a bit.
entity_default.txt
[ENTITY:MOUNTAIN]
...
[EXCLUSIVE_START_BIOME:MOUNTAIN]
[SETTLEMENT_BIOME:ANY_FOREST]
[SETTLEMENT_BIOME:MOUNTAIN]
[SETTLEMENT_BIOME:ANY_GRASSLAND]
[SETTLEMENT_BIOME:ANY_SAVANNA]
[SETTLEMENT_BIOME:ANY_SHRUBLAND]
[SETTLEMENT_BIOME:FOREST_TAIGA]
[BIOME_SUPPORT:ANY_FOREST:2]
[BIOME_SUPPORT:MOUNTAIN:4]
[BIOME_SUPPORT:ANY_GRASSLAND:2]
[BIOME_SUPPORT:ANY_SAVANNA:2]
[BIOME_SUPPORT:ANY_SHRUBLAND:2]
[BIOME_SUPPORT:ANY_RIVER:2]
[BIOME_SUPPORT:FOREST_TAIGA:2]
However, I usually also make "Playable Race Required: 0", because that allows some adventurer and dwarf races to die out during world gen and keeps that one hamlet from surviving massive pillages for two-hundred years for no reason other than it's on the "playable civ" list.
I don't see that that change would cause any problems.
I'll see what those changes do to the number of dwarf civilizations surviving. Maybe do some more tweaks if they are still low.
[EDIT] Well, that went well. Got 7 dwarf civilizations on the first run through (might just be coincidence). Pisskop will be pleased to know the world was still swamped with evil.