At all stages of the game for AD champions, thunderlord is less damage than an auto attack, every twenty seconds. For AP caster champs it is less than an auto until around mid game.
A single crit from Warlord increases attacks speed which grants you the extra hits to out damage thunderlord. It not healing off minions is a silly thing to say when we are talking about damage. Warlords out damages and gives a little bonus heal.
DFT straight out damages thunderlords if you can keep it on an uptime of about 1/3 to 1/2 of the time.
Fervor of battle, even at level ten will have done 220 damage just getting it stacked, and once it's stacked does ~40 damage per hit. So, if you can even just get it stacked and not keep it, you still outdamaged thunderlord unless somehow you manage to have over 400 bonus AD at level 10. The required bonus AD for TL to win that calculation keeps rising.
We could even be completely stupid and go grasp of the undying on a ranged auto attacker and it would still outdamage thunderlord till late game.
Tell me again how it's the best thing in the world when it does less damage than an auto attack.
TLDR, maths confirm you are seeing TL because it's easy to use and because cunning tree has really nice choices, not because thunderlord is stronger than other keystones.
