Raven Crowking said:Does that mean that we now ban multiple opponents against a single PC?
No.
The real problem only comes in with unanswered inits. For example, most of the time, if an NPC moves up to a PC, he only gets a single melee attack during the round that he moves up. Ditto for any other NPC opponents that move up.
If the DM has 5 NPCs do this, it is at most 5 attacks. On that round.
Unless you run all of your NPCs on the same init (which in and of itself is a fairly poor rule as well), typically either the PC or one of his allies will get an init somewhere within this timeframe. Even if they do not, you are talking a maximum of 5 unanswered attacks. Course, 5 attacks could be deadly.
However, it is not the 5 attacks that is super deadly. It is the 5 full round attacks where each opponent get multiple attacks each. For example, 15 attacks is super deadly against most PCs unless the opponents are fairly weak.
So, in an atypical but not unheard of case, a PC might have 4 or 5 opponents fighting him that he did not have the previous round. This can often (but not aways) be handled if all of the opponents moved up and only got a single attack each.
But, with back to back inits, if you roll all of your NPCs (or an entire group of similar NPCs) on the same initiative, then once in a blue moon, 4 or 5 NPCs will lose init on round x, run up to a given PC after he has already done his action, damage him somewhat, but then on the next round, the DM rolls a great initiative for those 4 or 5 NPCs and unless he fudges his dice rolls or "suddenly" has these NPCs for an inexplicable reason start picking on other PC targets, that PC is going to have 16 or more unanswered attacks against him (4+ in round x, and 12+ with 3 attacks per round medium level NPCs in round x+1).
It is the sudden "Opps, the Init Gods just gave me a boatload of attacks against the PC and he is toast" scenario. The DM did not even intend this.
Now granted, this can occur with the normal init system. It just happens a lot less frequently since a PC who was attacked by 4 or 5 NPCs would tend to get out of Dodge or cast some spell that wipes them out or perform some other action that limits how much he gets attacked. In the back to back actions scenario, he does not get the chance to do this.
The back to back actions scenario effectively short duration doubles the number of attackers against a PC and can more than double the number of unanswered attacks against a PC than the normal init system.
And, this does not even take into account back to back spells which can be even more deadly.
And unlike other multiple attacks / multiple spells scenarios, the PC and his allies cannot react to these. That is the real issue and the real reason it is a bad rule.