"I was actually doing very well playing the phoenix hero until my game client crashed (so I was the leaver)."
I hope that it wasn't hero attack that caused you to leave.
"I felt it was a little bit OP to have a hero that could pull enemies with +60% increased movement speed."
I definatly agree that the phoenix hero was OP in previous versions (especially graviton beam). However, I have nerfed graviton beam quite a few times over the past few versions so that it now costs more energy, has a longer cooldown and a shorter duration. The last nerf was in either 1.4 or 1.5 (I forget) where I decreased the duration by 25%. Since then I haven't really had any decent playtesting with the phoenix hero so I wouldn't feel comfortable nerfing graviton beam without playing some games with the phoenix hero. It is too bad that your game client crashed because I would have definatly liked to see how balanced the phoenix hero is.
"One of the main concerns that I heard was to reduce the difficulty of the NPC units, though, so if you do that then I think the phoenix hero will be more balanced."
If you are having trouble with the computer controlled units as the phoenix hero then I highly suggest that you use patrol micro. Patrol micro is where you move your pheonix, click patrol anywhere, and then move your pheonix again to basically attack while moving (you can use hold position or attack move instead of patrol if you prefer). Basically I modified the pheonix' attack (as well as some other heroes like the vulture hero, the banshee hero and the probe hero) so that this type of micro is possible. If you micro correctly then you should basically never be hit by computer controled melee units.
Edit: sorry, I misread what you wrote. You meant that if computer controlled units were weaker then the pheonix hero would be more balanced because graviton beam would be effectively weaker. Still, I'll leave the above paragraph up as a tip to other players.
As for other the concerns about the strength of the computer controlled units, I have definatly seen quite a few. Many of the concerns have been about the strength of the immortal (though a lot of these concerns might be purely psycological since the protoss recieve 1 big scary immortal per lane every 30 seconds instead of 2 less intimidating siege tanks or 3 hydras). In general, I wanted units to be relatively stronger than in DOTA so that players cannot carelessly A-move infront of enemy units and expect not to take significant damage. Currently, I like the balance between hero strength and unit strength in the early game, however in the late game heroes are a bit too weak for my liking. I am considering adding more levels to the heroes so that they are stronger late game. I am also considering increasing the spawn interval from 30 seconds to 40 seconds (though this is for a different reason, primarily I find that there isn't much incentive NOT to lane and do other things like gank or kill critters).
"I'd like to try the phoenix hero again when my game client doesn't crash, so send me a message if you need another test at any time. "
Okay, I will keep that in mind.
None.