Why are Pyke's base armour and MR so high?

The Phreak base stats thread got me looking more at base stats and Pyke's are weirdly high for his role/playstyle (support assassin right?). This is a question for why they are so high? not asking for a nerf, I'm more intrigued as to why his base stats are so high compared to other assassins.

He ends up having 130 base armour, the highest (15 above the next which is Braum and 30 above Malphite) at level 18 due to his high base and 5 per level growth (the highest). Also, he has the 2nd highest base MR behind Talon (Talon got a base MR buff a while ago), this is because his growth is 1.5 instead of 1.25 like everyone else who is melee (ranged have 0.5 growth), why doesn't he have 1.25 growth?

Is this just another way of forcing him to build damage because of his passive? Compensate him in such a way that he is safer than most other assassins because he has base stats comparable to Vanguards but because he can't build bonus HP, make him build damage because damage?