Desert Sun / Heart o Winter mechanics and question

[tinkthank]

Does anybody get these? (Obviously addressed at hot/cold nations players)
I like to have my nation have its preferred temp, and rather have it ahead of time too, but figure I must be doing something wrong:
-I figured that Desert Sun, for instance, would spread heat at a rate which is exactly NOT dependent on dominion (since the heat of the scales I chose is spread based on dominion), but am unsure. Or perhaps it spreads like a temple check? Does anyone know?

I dont feel that my heat is spreading as much as it should; I dont notice significant differences between my heat spread with DS and without it, whereby I suppose that "significant" should mean that it should spread out at a rate of at least +1 more heat/turn than it would have otherwise.

At 50 points, that is a whopping 1 scale + 25%; does anyone find it worth it? (Worth it = obviously dependent on the context (MP, SP, playing Abys vs Cold Nations, playing Abys vs. neutral nations, large maps, small maps, etc.); feel free to name when worth it and when not.)

Thanks much