@Keterys: I probably should have been (even) clearer.
I'm not disputing what the PHB says or that WotC did itthat way because they thought they would make us a favor.
@Urzafranz: And so you don't need to find any links. There is no need - I believe you.
However, what I am arguing is this is in no way easier. In fact, I think it makes it hugely more complicated!
Not only does is it completely gamist, and a complete disconnect between out-of-game rules and in-game "reality", but I believe the actual rules themselves will become an impossible mess.
Examples:
1) If you're both hit by a Freeze Bolt that Immobilizes (save ends) and Grave Bolt that immobilizes (save ends), one will completely override the other, despite them being completely different powers; one Cold and one Necrotic. According to the rules, you simply save against the most recent one.
However, this example is illustrative: if, say, you've got a +5 save bonus against necrotic effects and the Freeze Bolt has a -2 penalty on saves. Then you want to be hit with Grave Bolt last, because it gives you a relative bonus of +7 for your save.
In fact, with a scenario such as this, if you have an ally that can produce a necrotic Immobilizes (save ends) effect, you might even want to ask him to blast you in the face as this will automagically "erase" that difficult Freeze Bolt for you, replacing it with the much easier version of the same condition!
2) Attack A gives you ongoing 5 fire and immobilized (save ends both), attack B gives you ongoing 5 fire and dazed (save ends both). At the start of your turn you only take 5 fire damage, but at the end of your turn you (obviously) need to save twice. What happens if you save against the effect of attack A but not B? Are you still on fire? If not, are you still dazed? What if one of the attacks didn't have a rider effect? What if neither of them had a rider effect?
In all cases but the last one, you'd keep taking the ongoing damage even after successfully saving against one effect. In the last one, however, because you've got an exact match on the game statistics (regardless of in-game causality) saving against one also removes the other.
And yes, how is this good for the game?
I completely understand how people get confusing with a rule such as this.
And this is what motivated to write my post.
What is the benefit of introducing a special exception when it
1) is in no way related to what's actually happening in the game?
2) doesn't reflect "common sense" and thus is hard to remember?
3) generally confuses the hell out of people?
What is the actual benefit of this rule?
Sure, if you face lots of identical monsters, you're somewhat protected against focus fire (but not if they simply try to blast you to smithereens) but is this really worth it?