One of the elements in 4e that I don't think is handled well is resistances. The main problem in my view is that 'typed' damage should be more dangerous than 'untyped' damage.
It's one thing to get hit with a sword...but to get hit by a sword that then burns you (fire), or shocks you (lightning), or drains your life (necrotic) SHOULD be nastier.
But it's not.
The problem is that PCs realize that one of the ways they can reduce the damage done to them is through resistances. It's difficult to get resistance to 'all' (and as far as I know there isn't a resistance to untyped only) but it's easy to get resistance to poison and there's even a 10th level Wizard Utility power (Mass Resistance) which allows you to choose the resistance when used (and can potentially protect the entire party to boot).
However, most monsters and the Page 42 stats do not take resistances into account. Even worse, certain groups of monsters (yuan-ti, drow) or solos (any dragons) typically only have one damage type, and it's not untyped damage. Thus, a single use of Mass Resistance can turn a challenging encounter into a grind. This, in fact, is exactly what occured in our last session on Friday. The Wizard's use of Mass Resistance had made it so that none of the monsters could significantly damage anyone in the party.
One thing that struck me odd when altering the Elder Blue Dragon for my Monster of the Week post a couple of weeks ago, was that the Gore attack, which you would think would be physical, was only lightning damage.
Personally, I think something needs to be done about this. However, on the other hand you don't want to punish players who use their resources in order to prepare for an attack on a green dragon, or such. However, I think that the way the rules are in 4e, resistances move encounters that are challenging to grinds. I'd rather resistances be part of the problem solving in the encounter. One that would be dangerous, but with smart preparation, the party is able to handle the challenge.
I have two recommendations:
1. Add an untyped damage amount to those powers that involve some sort of physical attacks like claws, bites and the like. A perfect example of this is the Red Dragon bite. As for how much, a starting point would be the Low Normal damage for the appropriate level on Page 42.
2. Add 1 die damage per tier for powers that don't involve physical damage (ie the Young Red Dragon would see it's Breath weapon become 2d12+4).
The final question is whether or not there should be any changes to the other direction, that is, the monster resistances. I don't feel this is necessary. The PCs should have a good variety of damage types. Also those classes that do specialize in one type (ie the Infernal Warlock) have abilities that can either ignore resistances or they get extra damage when faced with a resistance against their prefered damage type.
Any other recommendations out there for dealing with resistances in 4e?