The goal of the 6-8 encounters is to exhaust the PCs' available resources. This includes HD from Short Rests & associated Short Rest recuperations that are 1-per-Long-Rest as well as those that recuperate from a Long Rest. So there's 2 or so Short Rests baked into this assumption. One way to deal with this is fewer but more challenging encounters where appropriate. Encounters don't need to be fights, either - they can be traps, puzzles, use of spells to bypass barriers, etc.
I'm running a Tier 3 AL mod soon and I'm looking over the encounters. The first one is a stand-alone during travel that can be immediately followed by a Long Rest. This means the players won't need to pull any punches and so I'm increasing the difficulty of the attackers enough to challenge a group of the recommended APL but maintaining the theme and purpose of the encounter itself.
Later there's a major encounter prior to the approach to the finale. Some parties would be tempted to do a Long Rest after this fight but I've annotated the encounter villain's monologue to include information that lets the players know that time is of the essence. They can rest but it will have major repercussions (a ritual is further along in casting than if they go straight on or take a Short Rest).
I know, lots of you don't want to have to do that work on a published product, it should auto-adjust or something else unattainable. Or you want to create a 'sandbox' where you shouldn't have to do this kind of balancing because it's not 'fair'.
The truth is, if you want to run a fun game with memorable challenges, it's on you as a DM to use your judgement, skill and imagination to make it so.
" Yes and sort of... To me the key as others noted is diversity... Sometime three heavies, sometimes no heavies but lots of lessers. Sometimes forced pacing, sometimes not. Sometimes the heavy is the first fight but you still need to push on thru weaker ones to get to the goal leading to very tired and "worried" PCs going more cautiously. Sometimes the major storms prevent short rests in the field. Etc etc etc. To me the real answer is almost always "there is no single answer" and keeping it. Diverse avoids many of the perceived problems from moving from challenge to problem.
