A) Ignore mr/armor since it is true damage.
You'd rather it be magic damage and do nothing late game because it doesn't scale?
B) Hard counter summoners heal, since A) Will give grievous wounds, and B) It damage naturally outescales it.
Not really a hard counter, but does weaken it. Heal will still save you from dying to Ignite if they can't follow up. Damage also always outscales defense. Game is meant to work this way. And for a good reason.
C) Hard counters heavy sustain champions, such as mundo, WW, swain because of the grievous wounds.
Get me better options and I'd have no problem with it not having GW.
D) Barrier will only get one tick of its duration.
Time your Barrier for the other damage you're taking that was meant to kill you.
E) Reveal invisible enemies.
F) Interrupts recall.
On a scale of 1 to 10 how bored were you when you wrote this?