IME, 5e doesn't require 6-8 encounters to be balanced. What it does need is the POTENTIAL for 6-8 encounters.
If the players know that the DM will only throw 1-2 encounters at them per long rest, then of course the paladin will outshine the warlock, and the fights will be easier, since they know they can safely expend half their total resources every encounter.
At my table, we tend to roll about 6 random encounter checks for each day of overland travel (4 during the day, 2 at night). The odds of having 6 encounters is extremely low. But we avoid going nova because there's always a chance. Lately, on most days we have 0-2 encounters. Some of those encounters might benign or even beneficial. However, the potential for a hellish encounter day means that we treat each encounter as though it won't be the last. We've had days where we were so resource drained by the end that we were forced to flee from the last encounter or two despite our best resource management, and no one at my table likes running away. It happens rarely, but rarely is sufficient to keep us on our toes.
Interesting that you mention that. I have long been opposed to including random encounters in my games, but lately I've been re-examining this stance as I prepare to launch a new campaign. This is good food for thought as I pin down what sort of game I'd like to run.