One thing I don't particularly care for is the power level (or even existence) of deities being based on their number of worshippers. Planescape hits that hard, and while I use Planescape as my baseline, I reject that point. Basically, the way I look at it, when you're divine, you stay divine, unless wrought upon by some other force. You don't need belief just to fuel your existence. I do say that your worshippers determine whether (and how much) you can exercise influence on a world or in a crystal sphere. And they might cause your power level to fluctuate slightly (but not enough to mechanically cause you to change status between demipower, lesser power, greater power rankings). With regards to powers dying due to lack of worshippers, I just say that a lot of people in Planescape areas believe they died because of lack of worshippers, but that's not really true. It might have made them vulnerable, but they actually got their head lopped off by another power that didn't like them or something. And I like the sort of stealth take 5e added that deities are just as able to return from the dead as mortals are. 3e Deities & Demigods contradicts the Planescape lore on that point in any event, and it's one of the rare cases where I go with an actual contradiction from 3e.