Trolls in fantasy games are the equivalent of birthday candles that won't blow out. I remember my first, frustrating encounter with them back in 1st edition. We kept hacking away at them, and they kept healing the damage we'd done. I think the first time I lost a player character was to a troll that regenerated faster than we could hurt it. My hatred of these things was palpable.
As a gamemaster I've very rarely used trolls in my game, especially against lower-level characters, because I'm not a "killer GM". Bumping off characters for sport isn't my idea of fun. In published adventures, I tended to swap out other creatures, usually ogres or hill giants, the types of creatures that equated to the trolls of myth and legend. I don't recall the things that lived under bridges and harassed billy goats having a healing factor like Wolverine.
Yet they are an iconic monster, and people expect them. There are players that actually like to fight them. So I needed to find ways to make them interesting, palatable to my tastes, and to give them some logical and rational reason for existence in my own campaign world of Desteon. That meant that I either had to make them into sympathetic characters, or weave them into the overall ecology in my world building. In Troll Hide, I've done a little of both. Hopefully, you can use this information to make the trolls in your game more than just a go-to hack-and-slash encounter.