No, there is already a massive drawback to invading. You are losing another player that could be DPSing the boss for more than 40 secs. This can slow the crap out of your DPS unless you are running a really melty team comp. In that case then they need to address what is melting the Primevals. I have tried invading into a team that is ahead and I got a few kills, healed the Primeval only for them to instant kill it after I teleport back. The primevals have WAY too little HP for a boss. There is no back and forth, its whatever team got lucky with more heavy ammo or have all their supers and a titan with melting point.