I'm considering buying Tyranny, but I'd like to be more clear on something.

Reading about the two DLCs (Bastard's Wound and Tales from the Tiers), it's not really clear to me what's part of the DLC and what's part of the patched main game.

I'm not really that interested in the random events, the settlement and the NPC quests. But I AM interested in new ending, more dialogue options, and more ways to influence NPCs.

What's part of DLC and what's part of patched main game? The descriptions on the store page are so vague. Can I read very distinctly somewhere what the differences are?

If it's more dialogue you're after, then you want Bastard's Wound, even though 90% of it takes place in another boring dungeon. However, it adds companion quests, which means more ways to influence NPCs I guess. It also adds a new ending. Tales from the Tiers is just flavour text that pops up during world map travels, enabling you to gain bonuses and items if you choose the smart answer.