His grab mixup is one problem, if you jump his normal grab still works(resetting the cycle) and his forward A does one hit of damage, if you stand still his blue grab woks and back A deals 1 damage, if you block both grabs would work - you simply cannot beat out his moves when he does this because he will hit on your first frame of vulnerability due to knockdown length.
math incoming As forward A doesn’t knock down I will factor it in to my calculations and assume he picks a random one of the three actions, damage is avoided when his bA is blocked, grab yomi’d or C jumped(1/3 chance), 2 damage and a reset occurs when grab or blue grab hit(4/9 chance) 1 damage occurs when bA hits(2/9). This means off of 1 grab loop there is a 1/3 chance of taking only 2 damage, a 2/9 chance of taking 3, a 4/27 of taking 4, a 8/81 chance of taking 5, a 16/81 chance of taking 6 etc. In short he has only a 55.5% chance of doing LESS than 4 damage off of a throw, 44.4% of 4 or more and a 19.7% chance of winning the round vs most characters(6 health, anyone except midori and rook himself) off of a single throw
This alone would be annoying at the best of times, but rook has a very safe approach, his B has super-armour and is only -4 on block, if you do anything other than a grab on or two damage attack after blocking he can execute his B or C and hit you. it should be noted that his B knockdowns and leads into his throw loop and his super armour is present even after he attacks so it is also safe on whiff. in other words even on miss or whiff his B forces the opponent to pick between two options and get punished if they guess wrong and the punish is his throw loop, on hit it is his throw loop
I could also mention his air moves having very few frames for a lumbering giant or having his jump C give him extra approach time. But the worst thing is that in addition to all this he has the most health of the game, In my opinion either his approach game needs to be seriously nerfed or his throws need to be toned down a bit to prevent the loop from being so easily fatal, I could understand rook being good at one thing, but he is good at everything except projectiles