The general consensus is that the game is remarkably well-balanced, but that your strategies develop as you do. It doesn't have to be perfectly balanced, since it's a game of two halves.
Initially, when you are new to the game, the trolls just swamp the dwarves.
Then, you learn how to make blocks, and the dwarves swamp the trolls. This seems to be the stage you are at.
Then you learn trollish aggression, and when and where to make the sacrifices as a troll to stop blocks building and to spread out the trolls, and all that's left is mopping up the dwarves that are left because there's no way they can make a block once you've got the trolls spread out... if you're fast enough.
Then you learn to make dwarvish feints to get the trolls to spread out in the wrong direction first, learn the triangle of death to kill them as they come in with minimal losses, and you're back to swamping the trolls... most of the time.
Then you get the right pacing to strike out to prevent blocks building anywhere, you appreciate that the diagonals are often better paths to tackle because they are closer in terms of shoving, you learn to never, ever retreat, and the trolls once again have the edge... just.
Further refinements on either side happen, but in the end, neither side has an overwhelming advantage.
The thudgame.com forums are sadly dead, and seem unlikely to be resurrected, but you can still find them on https://web.archive.org/web/20081021162429/http://www.thudgame.com/node/183 the search engine won't work there but the forums are fairly easily navigable. The strategy section has a wealth of good info.
The best advice, though, is to play lots of games against lots of people much better than you, and see how they kick your ass with the trolls. You will quickly transition to the next cycle of "how the heck can dwarves possibly ever win?" :)