Party optimisation philosophy

[LudicSavant]

The name of the game is resource efficiency.

As Max says, it's good to be able to vary your output -- The more dangerous an enemy is, the more efficient it is to use a nova. The less dangerous, the less efficient.

The mistake some people make is thinking that at-will abilities are inherently more resource efficient, which counter to many people's intuitions isn't true. The reason for this is simple: There are two sides to attrition, that which you spend to do things, and that which is spent by enemies doing things to you (like HP damage). If the amount of bad stuff an enemy would do to you exceeds the cost of your 'reduce them to microscopic particles right this second' option, then that nova option becomes resource-efficient, and not doing so will reduce the number of encounters you can take before resting (or someone dying or something).

Anyways, this is why, for instance, a party of 4 Champions generally won't actually last for more encounters a day than, say, a party of 3 Champions and a Life Cleric.

The one caveat I'd add is that I wouldn't draw much of a distinction between 'literally at will' and 'has enough resources to be drawn out throughout most or all of the day." So, basically what Eldariel said in the very first post.