Other Masteries Are Niche, Thunderlord Works For Everyone.
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Fervor, DFT, Warlords and Storm Raiders are only actually good on a select few champions whose kits synergize with them.
Fervor for champions who rely on autos like
Auto reliant ADC's (
)
DFT for D.O.T based champions like
(Still prefer thunders for the precision mastery)
Warlords for
and Auto reliant ADC's (even though early game it isn't useful at all since it takes awhile to achieve enough crit)
Storm Raiders on champions like

But you get the point, as you can see and hopefully agree with, is that unlike Thunderlords the other masteries are only good on a few niche champions. Even then those champions can still perform better with Thunderlords than the mastery which is optimal for them in theory. Brand, Yi and Xin can all take Thunderlords and still do very well even though one of the other masteries should in theory benefit their kits more effectively.
Thunderlords is universal and nearly never a poor choice, even when other masteries can and do do it's job better. So maybe, it should only be proc'd on spell casts instead of damage done. This way
and
wouldn't be able to proc it with just a single E, then in turn making players consider DFT to be the ultimate best option for D.O.T champions.
I am not worried about tanks taking Thunders because in reality they're actually doing themselves a disservice by not investing in %Damage reduction/300 Free health/Stealing 3% of your total health from the enemy.
: You can Q and then auto. If he has Unseen Threat ready to activate, he can proc Thunderlords just with that combo, since both the auto-attack itself and Unseen Threat count as separate effects for Thunderlords.
and