There is this cool ability of the spirit speaker called "Cloud of Mist". It reads: "Exhaust this card. While this card is exhausted, each attack that targets a space within 3 spaces of you misses unless the attacker spends 1 Surge"

Now, the dwarf in our group wears this cool armor-cape. It delets one of the surges you attacker rolled. Does this mean attacking the wearer inside the mist would cost the OL two surges???

As long as he's actually targeting the dwarf's space, yes I believe it would. Particularly harsh considering how much less frequently surges come up in 2E.

If he was targeting another space within 3 of the dwarf (that did not include the dwarf through AoE), the attack would only force 1 surge out, of course.