Late answer, but yes, yes you can. I have the same exact laptop as you and I used MSI Afterburner to overclock it by 135 base clock/300 memory. Frame rates went up by about 5fps on average. No extra heat issues. Completely safe.
https://www.amazon.com/G751JY-17-Inch-Gaming-Laptop-model/dp/B00NWE9RPA
This Asus ROG destroys everything else above, due to the 980m versus 970m in all the rest. I own it and it's great. Heavy and the battery life is poor, but performance is top-notch, and it runs VERY quiet and cool.
I play...
Sounds like the charger that you are using now isn't appropriate for the laptop, and it is kicking down to using integrated graphics instead of the 920m. Buy the right charger.
Asus ROG 751 with an i7 4720, 16gb of ram and 980m is one of the most powerful and fastest laptops for $1629 on newegg. It's a very good gaming laptop, but if you don't game, it will do well in intensive apps, too...