Thud! - Can the Trolls win?
I have found that it is possible for Troll to actually play a strong game, however, there is a fundamental issue with seeing that one could win with either the trolls or dwarves.

Remember, Thud! is an asymmetrical game--and in actuality a complete game comprises of what more closely resembles a "match"--a player plays one game as as each and the remaining value of the pieces are summed to determine the winner.

Thus, if you find your games really only feel like loss-minimizing--and lack strategy--the same applies to your opponent on his turn.

There isn't a lot of openly available games downloadable for analysis for Thud! as it is rather unpopular, but I'm basing this on my own personal play vs a computer opponent that I myself have designed: Thudgame on github. While the AI itself isn't an infalliable player, you might find that the Troll AI can often be quite threatening and I believe there's much that can be learned from it. 

Unfortunately, there's not much depth to the openings (the board is symmetrical).  Some common openings I see the Trolls winning with are pretty much one of these two moves:

 

It's not always the same trolls, but you choose your attack vector based on the initial dwarf move (whether you want to hit the dwarf-swarm or the side dwarves are neglecting).

There's a system in how well you can get a single troll to defeat far more than his own value (5 dwarfs per troll is winning), but I have a hard time generalizing it. Give the bot a shot and I think you'll see some winning patterns emerge.