Hello there everyone.
In the second part I suggest Riot buffing this Q sustain ability and I will comment why.
2) OK so his Q sustain is wayy to weak considered the cap limit that is given to him.
Unempowered Q at level 1 deals 60 damage and heals 5% from minions and 20% from champions. So lets count now:
If you hit 1 minion you will regain:
60 damage - 100%
X (heal amount - 5%
X = (60 * 5)/100 = 3.
That means you get 3 HP per minion hit. Wave consists of 6-7 minions. If you are lucky enough to hit all of them, you will regain 18-21 health. Champion health regain is 4 times higher (20%) so for 1 damaged champion at level 1 you will regain 12 HP.
Situation: You are at top lane. A minion wave (with siege) comes and a champion. You get in all of them use your Q and heal for 21 (from minions) + 12 (1 champion) and you maximum can regain 33 HP, while the cap is 50, and its literally impossible to reach that limit in top lane. The situation here is desribed how the events may turn out best to your favour and that happens rarely. Not to mention that if you take any minion aggro in the process your heal will be neglected because minion will hit you harder than you heal.
So let's remake your formula.
Unempowered Q at level 1 deals 60 damage and heals 5% from minions and 20% from champions plus an AD ratio of 0.8 having 72 AD at lvl 1 (runes, materies, an early attack damage item, etc). So lets count now:
60 damage + 0.8*72 AD = 117.6 = 100%
X (heal amount = 5%
X = (117.6 * 5)/100 = 5. Per minion
Y = (117.6 * 20)/100 = 5. Per minion
5 HP per minion hit. If you hit 5 of them you'll have around 25hp and if you hit the champion you'll have 23.5hp more, then you are close to cap with 48hp (hitting only one champion and not all the minions of a wave).
I will be glad if you reconsider the importance of the AD ratio next time before calling a nerf. Actually I hate the health restored harassing Renekton because he hurts me more when I can't heal myself.