You are likely moving all of your units at once or in bunches. Try to move them in groups of 1000 around the map. Its a brute force method but you will win eventually. If I were you I would revisit the single player games and work on those until you have improved your ability.
Wait a sec, I got something wrong. I meant to put the Troll on one team as an AI and the player and all the others on the other team. I've done that now, and then we'll see if it's winnable...
If your level is high enough, you can use Airlifts if you want.
I won too. Hint. Diplomacy cards are useless as well as blockade cards. You should keep fight. Each time game give bigger reinforcement cards. You should not keep all yourself. keep reinforce your allies If most of them survive you can win easily.
cookie - those are abandons, not blockades, and are super-useful for wiping out large stacks (assuming you know where the enemy will move next). Otherwise, that's good advice.
Vexos, I believe you. However, you can't share single-player games like you can with MP games. Try to click your own proof, and you'll see what I mean. instead take screenshots, for example, if you want to share