Scouts, particularly cloud scouts, are basically set up for fighting invokers (relative to a zerker).

They are less set up for fighting warriors (relative to a zerker).

One thing I would consider is using the spells that change your terrain more though.

e.g. Conglaciation, quicksand (yes, I know he flies), gel, and the poison and incendiary clouds.

However, I think if you really want a decent chance of winning against a combo like that, you need to stop relying on voker magic and start relying on stuff that you get from scrolls/talismans/wands. e.g. Plague, crimson scourge, gas breaths etc. Couple these with gel, for example, and you could make things much nastier for him.

Sure, most times you'll still end up running, but sometimes you will actually accomplish something in the process.