Note: this is NOT about weapon balance. Don't talk about the Hellreigel, RSC, etc, I know those are considered unbalanced. That's not what I'm talking about.
Fundamentally, what does decreasing the time to kill (slightly) mean? How does it affect how a fight plays out?
Well, what it really changes is your margin of error when fired upon. A longer TTK gives you time to seek cover and avoid incoming fire. The longer the TTK, the easier it is to survive enemy fire, and the less effective getting the jump on someone will be since they will have time to run out of your line of fire. Combined with the buff to bipod LMGs, I can only conclude the intention here is to create gameplay where supports lock down fields of fire with LMGs that Assaults can't just bunny hop or twitch shoot their way out of. It also means that if you get ambushed/blindsided by a hidden/flanking opponent, you're probably going to die.
This means two things have to change in the way we play:
1. You must be more careful with how you advance. You must think about where supports can set up, where the fields of fire are, and the routes through the map that minimize exposure to firing lanes. If this isn't possible (it isn't always), then your team needs to be able to counter static enemy defensive positions with their own machinegunners, scouts (particularly effective against bipod users, it must be noted), good grenade/mortar placement, and gas/smoke grenade usage. In other words, an advance requires a bit more finesse than simply running forward and hip-firing anyone you see with the Hellreigel.
2. You need to be aware of where you teammates are and whether a given route through the map is covered; an open movement route is one that can be used to flank, and now that flanking is deadlier, that's something you want to avoid. You need to cover all bases and have control of your frontline, not be rushing around in a mob that can be manuevered around.
I will agree this change wasn't really needed, but nothing that's really changed from this TTK update is terribly taxing or arduous; it's just asking people to be a bit more careful and a bit more observant of the map and where they place themselves and how they move through it. I realize positioning and movement are often not prioritized by many people in FPS in favour of the holy recoil control/aim/twitch reflex trifecta that is considered the hallmark of skill, but I see nothing wrong with making it necessary in a game like this.