Chaffs do affects missile performance. Not once I fired one which was decoyed somewhere.
However it happens mostly in case of older system like OSA, TOR (here harder).
When I fire missile from OSA, TOR I just lock you by pressing enter key. I do not follow your miserable - in few seconds - plane via optical sight (aka "zoom") :D
Sometimes I trolled people by turning stuff on when they were happily flying close to me so they didn't have chance to quit.
Another thing was riding Tunguska and taking cover by high civilian buildings :D Poor GheyTens, Frogfoots couldn't hit :D You just moved out of the corner, fired and hide back.