Actually, I think it's more likely for trash AOE packs. Tank swaps are fine if your tanks aren't selfish.
Vengeance was also changed that if you have 1 mob, you get 100% vengeance from it. If you have 2 mobs you get 100% vengeance from mob 1, and I think 50% from mob 2. Then if you have 3, you get 100/50/33 in a 1/n situation. This is going to cause a HUGE drop in vengeance for AOE packs and fine, holding aggro on that 1 mob is easy but like the 8th mob? That's a pain the arse especially when your vengeance is going to be slashed.
Should also say, more threat isn't going to help tank swaps, because you're both going to receive the bonus threat. If only one of you did say for 5 seconds after a taunt, fine. But no, it's at all times. It's like putting 2 identical midgets on 2 identical boxes and saying "I WONDER WHO IS TALLER NOW?"