I don't think its designed to "encourage single class" characters. I'm pretty sure that's backwards thinking - single class characters are the default. That's why multiclassing is an optional rule, not the default. There are a couple limits in place (no stacking Extra Attacks outside pure Fighter) to prevent it from being completely broken one way or another, but its not exactly extensively tested and balanced.
The game is set up in a series of milestones. Level 5, level 11, and level 17 there are significant jumps in power as you leave apprentice levels for hero levels, then to paragon (orwhatever 5e calls them) to epic. This matches access to level 3 spell, level 6 spells, and level 9 spells. All 12 classes are built around these milestones, and these significant jumps in power.
When you multiclass, these milestones are still tied to pure class. That part didn't go away. Its part of the game design. So, as a direct result, MCing is actually only good for dipping, and a true half-and-half multi-class.
The game is set up in a series of milestones. Level 5, level 11, and level 17 there are significant jumps in power as you leave apprentice levels for hero levels, then to paragon (orwhatever 5e calls them) to epic. This matches access to level 3 spell, level 6 spells, and level 9 spells. All 12 classes are built around these milestones, and these significant jumps in power.
When you multiclass, these milestones are still tied to pure class. That part didn't go away. Its part of the game design. So, as a direct result, MCing is actually only good for dipping, and a true half-and-half multi-class.
