I don't know who you guys are playing with that Thunderlord's is still overwhelmingly popular. For such a generic mastery it's being used on pretty much only the people with nothing better to pick at this stage. Here are a few random team comps:
Top - Fiora: Grasp of the Undying
Mid - Lux: Thunderlord's Decree
Jungle - Lee Sin: Thunderlord's Decree/Strength of the Ages
ADC - Lucian: Fervor of Battle
Support - Janna: Windspeaker's Blessing
You've got a burst mage mid and a ganking jungler that requires snowballing to be of use choosing TLD and even then it's very possible that Lee Sin is making a poor choice in not opting for Strength of the Ages. Lucian, despite easily procing TLD when he wants to, makes another choice, and Fiora is taking a superior 1v1 mastery for top lane. Janna is obvious.
People are so out of touch when it comes to Thunderlord's. It's a completely balanced mastery that is only taken on multiple members of a team in very specific team comps where the champions don't work any better with anything else. An example would be Riven top, LeBlanc mid, Kha'Zix jungle, Lucian ADC (he would be making a suboptimal choice even here) and Morgana support. You've got three assassins, a bursty ADC and a support with no better keystone available.
Of course, you'd never get a team comp with 5 Fervor or 5 Windspeaker's because almost every keystone is designed to appeal to less champions than Thunderlord's does but as has been said many times before, Thunderlord's being generic isn't inherently problematic.