Wraithknight...I dunno. There's no disputing it's good, and as Denzark points out, somewhat undercosted.
But on a personal level (feel free to disagree and pour scorn and derision upon I), I just can't get too scared over something that can have it's last gasp stolen by a feeble Heavy Bolter.
I feel once you get to Super Heavy, the disparity between Armour and MC goes entirely. At that point, both keep on keeping on at full effect until they're destroyed. But Super Heavy vehicles typically enjoy being able to laugh heartily at all but the heaviest of weapons, of which there are typically blissfully few. Hence my fanaticism for the Ordinatus. That shield is brilliant. Tends to mean that in the first turn, your opponent can't scratch your paintwork, giving you a shooting phase or two depending on who went first, to thin out the numbers of guns that actually can hurt you somewhat.
Plus, Super Heavies are completely immune to Fleshbane weapons. GC are a tough target for them, but we all know the Dice Gods do love Sods Law....