I changed a couple of laptops to newer Intel AC wireless cards a while ago - one worked fine & the other was behaving in a similar manner to what you are describing. Messed about with drivers without any change & finally went back to the old wireless N card.
While searching for a solution to this I did note that there are some Intel AC drivers that are problematic & that reverting to an older driver often resolves issues.
Don't know if it applies in your case, but maybe helpful.