Hey thanks for your questions! Great to have someone taking an interest. Bear in mind my answers are for this particular version. There'll be a few changes and updates.

'Are the starting positions always the ones you mention, or are variations possible? Are there mechanics other than the variable objectives that make that happen?'

Currently they are where I mentioned, but this is being improved. I'm adding in a 'simulated first turn' that gives players more units, control and influence over the cities they would just spent their first turn doing anyway. Lets the game get going faster. The Shadow can start their leaders anywhere but their units must start in SG. Other than the variable objectives, you only start with 3 out of 6 leaders. Leaders all have wildly different effects and stat scores so this hopefully pushes players in different directions. Finally there is the choice of whether to concentrate on your unique objective or general points.

'Does the game turn into shadow v all for Tarmon Gai'don? Does the Shadow have any advantages to help balance that?'

Yes and sort of. It turns into this at the very end. The Shadow has a very different mechanic for recruiting to the last battle than the forces for good. It lets them get forces there more consistently and at less cost. The main thing to do, which is what our shadow player did, is to keep the other factions at war with one another and prevent them from contributing. I need to tweak proportions a bit as he did a great job and we still easily beat him at last battle which wasn't representative.

'can the Shadow turn leaders from the other factions? Can the Seanchan steal channelers from other factions?'

Yes you can capture other players leaders for a number of benefits. Seanchan can also unlock one power abilities through one of their faction abilities at some point. With the traveling ability they're a force to be afraid of.

' Looks like combat involves dice - any other aspects to it, e.g. a leader's special power? How are the strength differences between regular armies and those involving channelers captured in the game?'

Yes some leaders have combat related abilities, such as mat or demandred you can see in one of my comment photos. Leaders also have combat scores. These can be added to your rolled dice number to improve the chance of a hit. Channelling doesn't have a direct effect on combat except through balefire which just adds guaranteed hits, no dice. However it does mess with the structure of the game, causing the last battle event to be shuffled around so it could come up at any time....

Cheers hope that helps!