I would amend the above to say Gloranthan Trolls are different. Very different.
You can play with Trolls that are of any type in any world you create. The MRQ2 system does lend itself to a sandbox game. I have played in a game where the Harn world was communicated very well through the rules, including an encounter with a huge, ancient riddling Troll. We took the bargain instead of going toe to toe with it.
That said, Glorantha Trolls are awesome. They have a deep cultural perspective that is as disturbing as it is awesome. To begin to research it, is to begin to want to play one as opposed to fight one. Seriously.
And even without the regeneration, they make fierce foes in any encounter. In fact you have to pepper in a couple of trollkin to keep it even. A true Troll party in an honest run-in with an evenly skilled human party is probably going to do some serious damage, especially in close quarters. But even their slings are deadly.