I agree. DM is faster and hits harder. That's why I'm not excited about Reavers sooner; they are just so fast and hit so hard. Overlords are pretty stupid and slow. I've also had Behemoths that early or around that; maybe 6 or 7.
Yeah Behemoths start appearing from level 5 with MMM. That's one high-level encounter that can occur at any time at the moment.
I've experimented with this in my game, changing the creature leveled lists to spawn weak and tough spawns at all levels. I changed it to just spawning weaker creatures at earlier levels with the tougher creatures appearing later but keeping the chance of weaker creatures spawning as well just to keep the variety. It was the lack of variety of spawns after about level 5 which made me alter the lists. I like seeing the occasional molerat or ant in the wasteland instead of nothing but Deathclaws and Yao Guai and Radscorpions over every hill.
If you're using MMM weaker creatures will always have a chance of spawning at higher levels, though for areas with defined Encounter Zones they will still apply a minimum as they should. Wasteland, however, has no Enounter Zone so you'll always be able to see molerats up to albino radscorps.
Having high level creatures spawn at low levels though, its not so much the player who would have trouble with this as they can outsmart it, it's the npc's. I had a high level albino radscorpion spawn near the supermarket and it lay waste to everything in its path. It took a group of outcasts and myself to eventually kill it but I was the only survivor. Personally I do like the challenge of high level creatures at low levels but it was not fun seeing half the npcs mindlessly run up and mêlée this creature that they obviously had no chance of killing. Perhaps instead at lower levels a weaker version of the same creature could spawn so there isn't this reminder of your level when you start seeing the higher level creatures.
This is true, we could well see local populations decimated by the odd high-level creature. I can look at weakining these encounters when they appear, or perhaps that's just a side-effect of the dangerous world of the wasteland?
I think, at a least, I'll halve the chances for SMs and Ghouls unleveled spawns to appear, given their volume of spawning.
This might be more a problem with the NPCs in that situation. If NPCs entered a sprinting flee mode when the albino scorpion started its attack, it would probably be a more realistic reaction. Faster and more intelligent NPC fleeing is probably one of those things that would work well with static spawns. It could also reinforce the idea that you have to pick your battles in the early part of the game, and choose when to retreat and come up with a different plan. If the player sees a group of Outcasts sprinting away from an albino radscorpion, it would probably make them think twice before going in with guns blazing. It would also be a bit hilarious (in an "I'm glad that's not me" kind of way).
This should probably happen to some degree but I haven't checked -- MMM makes NPCs more likely to flee, especially if wounded, and the engine uses level difference as the primary driver to determine when to flee. As a high-level encounter would be a huge level gap, they should flee naturally without much prompting. The only tweak I might make is to lower the flee-check timer to give them a chance to register for fleeing before they get whacked. This is actually quite a long delay in vanilla F3, and is already shortened in MMM but I might lower it further.