In my opinion, it's not that I overrate thunderlords but that I don't have a better option.
E.g. I predominantly play J4 top. CotC is pretty garbage early - if I land E-Q I'll get a small shield that denies some of their trade back, which probably just means they'll run straight back instead of trying to trade back. Then CotC has a 45-30 second cooldown versus 25-15seconds for TLD, so when my E-Q is back up my mastery isn't. That's all assuming I want to engage with E-Q - most of the time I don't. E is on a relatively long cooldown (13 seconds at rank 1) and E-Q is my only escape. Q is only a 10/9/8/7/6 cooldown and is maxed first, so it's on a short cooldown and can be used to harass while not being lost for escape, so my typical trade is to let them come up to CS and use a passive enhanced AA, Q, AA for a TLD proc, taking a single AA in retaliation. I agree that CotC is much stronger late game, but in early lane TLD J4 is a massive bully against almost all matchups while CotC J4 is bullied by almost all matchups. TLD isn't exactly good for J4 though, it benefits most other champions a lot more. It's just something he can still make good use out of, while most other masteries don't help him early.
Also, I think the Cunning tree offers the best earlier choices as well. I want the extra CDR early and to break the cap late. Dangerous Game and Merciless are often the difference between dying for free to a risky gank and turning it in to a double kill for yourself.
Second example is I play Ahri Mid. Again, TLD isn't really good on her. She can get off the 3-hit proc, but it's not exactly easy. She either has to land charm (in which case the extra damage is nice for an all-in) or needs both sides of her Q plus an AA. Either case she's extending a bit extra in order to get the proc, opening herself up to more damage than necessary. She isn't really a great TLD user but nothing else works for her at all.
I honestly don't like TLD on most of my champions and yet run it often. It works well on Quinn (AA, E, AA) and I like it on her, but after how easy it is to proc it on her it feels a lot worse on everyone else. However those other champions still run it because there's nothing better for them. I hope TLD exists in the new system, but better options for these champions exist as well so Riot can see that TLD is popular not because people like it but because it's a catch-all when everything else is useless.
