Why is Trundle allowed to heal virtually ALL of his HP with a press of a button?
Not only that, but steal stats away too? Tone that down a bit, please.
Not only that, but steal stats away too? Tone that down a bit, please.

because fighters are ball of stat champs who counter ball of stat champs.
Because he's "easily kited"
Except not really if you build cdr and get e at like 6 s cooldown.
His healing is enemy %maxHP based, so it's not possible for him to heal "virtually ALL of his HP" unless he didn't build any and ulted a 60 minute Sion.