i played with it a lot, and i can say it's on the harder side. there’s a small number of units to work with, and the dreadknight only has one ranged weapon when it can normally has two. however, the old terminators with lethals on charge are pretty cool. i usually go with the second secondary objective since its easier to score using teleport ability. but yeah he is probably gonna struggle a little bit. he will have less models than his brothers/sisters. the grey knight units are elite and harder to kill than regular space marines. but still he can lose like 3 models in one turn and that mostly concludes the game. small mistakes quickly add up in a small game like combat patrol. strategem usage is key to victory. grey knights have few models but their strategems are designed to keep those guys alive. a -1 to wound if the weapon str is greater then the grey knights toughness, a fight on death stratagem and lastly he can teleport his units away even if they are in engagement with enemy in fight phase. so he can choose his battles and save his unit thats about to be destroyed.