There never was a meta in which everything was viable. I have to disagree. If you didn't have a good Fusion Rifle and a Vex/Suros... Well, you didn't have those. And at an equal skill level, you will lose to that combination every single time, if you do not have them as well (vanilla meta). Buffs and nerfs happened long before Trials ever came into existence. You overstate the importance of Trials. 6vs6 modes are the most played ones, and balancing mostly caters to them.