Since the encounters are so infrequent the players can just expend all their resources against each encounter!
Primarily my experience has been with 1st edition and the encounter tables therein. This cannot address his issues with Tsojcanth. But it can explain why wilderness encounters are interesting.
Number encountered and % in Lair: Both these values are astoundingly important. First, if the monster is in their lair, then it's not just a random beast, it's a decision about crawling in a hole in the ground. Second, being that these are random encounters, the full brunt of the number appearing tables from the monster manual come into play. Which leads us to our second point. . .
Distance and surprise: Have you noticed the encounter distances are longer? Elves do not like trespassers. Elves are all proficient with ranged weapons. Say you encounter (2d10x10) 90 elves at a distance of, lets be generous and say 10".
What party can survive 90 short bow attacks per round.
In fact, in what world can going nova allow any party to survive that encounter.
Let's look at some common number encountered for wilderness encounters.
Bandits: 20-200
Hobgoblin: 20-200
Berserkers: 10-100 (I'm sure parley will work great with these guys.
Science forbid you run into a buccaneer! 50-300 of those guys.
Ok, what about non-humans?
Wild Boar: 1-12 . . . with a movement rate of 15. An enemy that does 3-12 damage that you can't escape from?
Bugbear: 6-36
Crocodile: 3-24
Dragon: 1-4; You come across 4 black dragons. Nova that, bitches.
Eagles, Giant: 1-20
Preyton: 2-8; No, doesn't seem like much for creatures that are immune to normal weapons, attack at +2, have 4 hit dice, fly at 21" and do 4-16 damage (average of 10) per round.
Stirge: 3-30
All of this leads to the final factor, which is Pursuit.
Thankfully, because this was actually used in play, encountering something faster then you isn't instant death. You have an 80% chance to evade something chasing you.
-20% if they are faster
-50% if you're on a plain, desert, or open water
-30% during daylight.
Just, wilderness encounters are terrifying. Some things are easy (Dinosaurs), many things are not.
