Aggro is not harder now than 2.0, it's just now tank try to dps more, so them want to get a strong aggro directly to focus dpsing.
It's not like Tank was not able to do better dps before, but in 2.0 you was not realy forced to do this exept the hardcore raider who wanna dps higher to finish earlier.
There was already some STR war doing that.
I am sure it's why SE Make the raid in 3.0 forcing the tank to focus dps.
To have seeing that before 3.0, i saw one STR war most of the time not on defiance in T12 for exemple and also STR war on T13.