The Multiclass Trap

I was reading WoTC's Bruce's article, Wizard With a License to Kill, and my whole feeling of how multi-classing fails to give me a satisfying feel came crashing down on me. In the article, Bruce describes how he feels a "spy mage who is good with a dagger and stealth" works within DnD Next's mechanics. Here's how it goes, roughly, in my own interpretation and words:

You pick an overall background for your class, which I am assuming is like backgrounds in DnD4, a package of skills, possibly some abilities, and most likely nothing that improves as you level. That's all well and good, and pretty cool for a D&D character. Allrighty, let's get to the multi-class part.

Let's assume a superspy level character, and hit a full 20 levels. We want to be more mage than rogue, so let's do 15 levels of mage, and 5 of rogue. Ok, cool, we can cast like a level 15 mage, and fight like a 5th level rogue plus about 15 levels of weak combat modifiers of mage.

Let's put this character into a group of other 20th level characters, and toss them into a 20th level dungeon. Well, first thing, this character doesn't fight as well as the 20th level rogue, and can't cast spells as well as a 20th level mage. Trade offs, right? Well, yeah, but most players expect their multi-class creation to fight as well as a similarly leveled rogue and mage, and be able to keep up and contribute. Especially since monsters are balanced against pure-build characters equal to their level.

How we feel, and how SBRPG does it differently, is if your job relies on using a dagger, casting a spell, or using a skill - you perform that ability with a modifier equal to your class level. It's part of your job, thus a Class Skill, and it is locked to your level (plus modifiers for ability scores). A 7th level thief swings a dagger and picks a lock at a +7, just like a 7th level warrior swings his sword at a +7. There are no skill point systems or combat modifier progression charts, it's simple. Your level plus ability mods is your DRM if what ever you are doing is covered by your class.

The whole disconnect in d20-style systems with "skills needed to perform your job" and your level has always been strange, and gets worse when you put a disassociated skill-point system on top of it like in 3.5 and Pathfinder. If I am a 7th level thief, shouldn't my level describe my ability at being a thief? Otherwise, what does level describe? Why do I need to spend separate skill points to buy my "essential thief skills" of lockpicking and stealth?

We love all the games mentioned above, don't get us wrong; but we always felt that some of the systems in them do not play very well, such as combat modifier charts, multi-classing, or large skill point systems. They do not feel natural, and seem like design cruft held onto throughout revisions and editions. We designed SBRPG from scratch way back before DnD 3.0 with a simple truth:

3d6 + (Level + Ability Mods) - Challenge Level

Meet or beat a 12

Everything else comes from that.