his stun is only 2 seconds at rank 5 and it begins at 1 with .25 /point increases
if he mains his W, his damage will be low and he will also be within easy to punish distances. He is also extremely easy to gank, has some of the lowest burst damage in the mid lane
Q: 240 + 65% ap rank 5
W: if you go for gold, your damage is: 45 + AD + 50% AP ; if you go for blue: 120 + AD + 50% AP
E : 155 + 55% AP
and his ultimate has no damage
altogether at level 18, his damage can basically be at max 4(if you get that many auto atacks)(AD) + 395( minus 155 if you do not get stacked deck) + AP(1.2 minus .55 if you do not get stacked deck)
even with lich bane adding 75% AD and 50% AP(then add 2 procs of it) and thunderlords, the total comes to
5.5AD(from 4 auto attacks + lich bane) or 424 physical damage + ( 615(if blue is chosen and all abilities hit)) + 180(thunderlords) + AP values (2.70 from abilities and lich bane) and then let's add luden's echo just because 100 + 10% AP
you end up with 1319 + 2.8 AP value
if by some miracle you get enough gold for a full build and around 600 AP, this comes to 3101 HYBRID damage before defenses
this may seem impressive, but let's take it against a marksman without damage reducing items
with caitlynn's base stats (if he could even get into range of her), his physical damage would be reduced by 46% on her base armor alone and then his magic damage would be reduced by 28%
when you consider that, his damage comes to against caitlynn:
233 + 1927 = 2160 and that's against a caitlynn with no defensive boosts and requires that the twisted fate be within auto attack range FOUR TIMES! unless he goes into battle with his stacked deck ready, which requires time and targets and even if he does go into battle with it stacked, the damage will be the same just a higher initial trade
Caitlynn's base health at 18 is 1884, so if she has NOTHING, it will kill her, but realistically, twisted fate is sub-optimal to many mages who are not required to get into that range and stay in combat for that long (at least 4 seconds)
his value is in his utility, providing sight of junglers, splitpushing, crowd control against engages and a mild poke damage with long range
Edit: I forgot to add in thunderlord's 10% ap rating, but the value is minor at 60 damage
edit edit: it is too late and my math seems to have run astray, but it should not deviate too far from the intended point but I apologize
total damage = 5.5 AD value(lich bane included) + 180(thunderlords) + 10% ap(thunderlords) + 100% AP (lich bane) + 515 (abilities) + 1.70 (AP) + 100(luden's echo) + 10% AP (luden's echo)
and then multiplying by the variances of the hybrid types