DOTA2 fps drops in team fights any suggestions?

it happening for some time now but it did`t be fore or not so much i noticed, my temps are ok and i did blow out dust and reinstal OS and game ofc. but problems is still happening i think is after one path but i cant remember now 4 sure. and i did try lowering spec but drops are still there often below 25fps and in really big fights 19.
spec:gts 250, amd phenom 9650 4gb ram win 7 ultimate 64.

i did notes in task manager that dota use about 60% cpu at bast of times but then again i am not sure..