I've been thinking about Magic: the Gathering lately. One thing I've been musing about is the complexity of "fat" creatures, that is creatures with toughness greater than power.
For reference, creatures in Magic have power and toughness. When one creature blocks a second creature, they deal damage equal to their power. If that damage is higher than the toughness, the creature dies. Two important differences between Magic and Hearthstone. First, in Magic the defender chooses which creatures block (or not block) which attacker. Second, damage done to a creature is wiped away at end of turn. It isn't permanent like in Hearthstone.
In any case, consider a very simple board. Jane has a 2/2, and Sally has a 2/2. Jane attacks with her 2/2. Now Sally has a choice: she can either take 2 damage, or block with her 2/2. If she blocks, both creatures will die. It will be an even exchange of material.
A similar situation happens if Sally has two 2/2 creatures. She can block, but will still exchange material.
However, let's consider what happens if all the creatures are 2/3 creatures. In the first scenario, if Jane attacks, Sally simply blocks and both creatures bounce off each other. There's possibility of a simple exchange here.
In the second scenario, it becomes foolish for Jane to attack. Sally would block with both 2/3 creatures, and kill Jane's creature without losing one of her own.
Simply adding that extra point of toughness makes exchanges less likely. But exchanges are good for the game. They simplify the game state. The high toughness creatures lead to a more "stalled" board, which becomes more and more complicated.
High power doesn't display this. If the creatures where 3/2, exchanges would be just as prevalent.
I think it's good for PvP games to be able to exchange resources. Otherwise, the board state builds and builds, until one side gets a sudden advantage and overruns the other side.
I think healing plays a similar role in MMOs, especially PvP. It prevents the exchange of material until a certain threshold is met. For example, Eve PvP might be more interesting without logistics ships. An outnumbered force could attempt to come out slightly ahead in each exchange of material.
But with healers, you either have enough firepower to get past the healing, or you don't. Or you have enough crowd control to disrupt the healing long enough to kill something.
In any case, evenly exchanging material in PvP is good. Anything that makes exchanging material harder, even as small as a single point of toughness, should be considered very carefully.