yeah you have to wack it either with melee or range wep. I play on the same spec machine as you, all be it an AMD 4200 Dual Core CPU (very old now). I play 4 shaman and a 70 hunter which is instance grinding at the mo. you might have a few problems past 45, it just depends where you go. Me personally i go to Scholo @ 45+ coz i can sit my shaman on the bridge, clear the first 3 rooms and reset. My alts dont even have to follow. Its about 25 mins a run and ur get roughtly 1 level every 1 hour 30 mins. Its boring as hell, but it is very easy and i dont worry about agro, 1 / 2 levels a night goes quick.