2v2 shows "attacking" icon for everyone

This one tricked me.. i started to build def because i just looked at that icon and though: oh, i need to def!

[dcode]

There is an "attacking" icon? What exactly do you refer to?

that thing which appears when game starts, it flashes, its a "!" mark i think? it appears there where creeps will come.

[dcode]

Do you mean the start segment marker (/!\) ? This just marks where the path begins so you won't build on the wrong end

yes. i think its confusing in 2v2 when it alerts about incoming creeps, even when there arent coming anything anytime soon...