Character Stats, XP and Difficulty scaling design thoughts?

Skimming through the web for relevant info on scaling in games I came across this article:
http://onlyagame.typepad.com/only_a_game/2006/08/mathematics_of_.html

The article specifically is talking about XP, but difficulty has its place in there as well. For those of you that have finished games that implement a game that has enemies which grow in difficulty and have increasing stats as you progress - what were your thoughts on designing your systems for this?

I suppose there are a few ways to design difficulty and depends on a lot of how you're actually implementing your enemies and such... for instance if you just have five different enemies with unchanging stats, but you only spawn the strong ones toward the end of the game versus something like having one enemy prefab that grows based on either time played or player level.

Thoughts on the topic?

 

Difficulty increases solely in numbers is boring - Difficulty via introducing new mechanics or ways of approaching enemies is much more fun. Obviously implementation varies drastically depending on gameplay, but a general good pattern is:

Introduce a mechanic / defeat method on a single enemy
Let the player figure out how that method works against a smaller number of these enemies.
Ramp up the difficulty in applying that method, with a larger number of enemies or stronger foes,
As the player approaches mastery (but ideally before they reach it), repeat the process with a new mechanic.

You can continue to re-use and mix in older mechanics as you increase difficulty. An example I can think of would be Ryze. You initially get basic enemies, which you can defeat however you want. Add in stronger foes that block your attacks, and you need to parry them to get an opening. Add in foes that use powerful strikes to crush your parry attempts, forcing you to dodge them to gain an opening. Add in foes that dodge your attacks and recover from parries quickly, forcing you to corner them or force an opening. Mix enemies together so you need to combine dodging, parrying, and hyper offensive to keep up. The stats of the enemies scale relatively evenly with you, but the mastery required to defeat them continues to increase, resulting in a satisfying challenge throughout the game.

 

That is a good point about the boredom factor with reusing enemies and scaling values like that.

In the case that you do want to reuse an early game enemy later in the game without having to create a new prefab and database table, the scale system would need to be effective. Depending on the number of enemies in the game I'm not really sure which way I would lean on that matter.

As an example look at Risk Of Rain, they reuse a large number of enemies and they scale with the difficulty level. If your character hasn't developed enough - fast enough - then they'll eventually start crushing you. I think thats a different type of system that isn't really commonly seen though. Typically its much more along the lines of what you're talking about, and the reuse is frowned upon. Personally, I didn't think it was a negative thing in the case of RoR but could definitely be a negative impact if not done correctly.