In T1 heroics, if you don't have at least 120k potency, you're swinging wet noddles at the mobs...
For raid people should get a minimum of 130k potency, but aim as high as you can get.
You WILL need to plat infuse your gear (including your quest gear) to reach that potency. If you don't, however, you won't be able to contribute towards killing the mobs.
Also, your ethereal armor and weapons from CD can be infused beyond last expacs caps, to be sure to improve those as well.