Wait, you prefer multi-class characters and you don't like the conversion to 4e, but don't have a problem with the one from 2e to 3e.
How?
I mean when I first played 3.0 it was with a group that converted our existing characters from a 2e game to a 3e game, and then played the same game session from our 2e game in 3e. We were worried that the conversion wasn't good, so we thought we've give it a try and see what we needed to tweak to get similar results. We had two elven multi-classcharacters, a Ftr/Mage and a Mage/Thief, and I think it's fair to say neither player exactly enjoyed the experience of having horribly gimped PCs.
It's amazing how much of what we felt was wrong with 3e came out in that game. Converted straight from 2e according to the guidelines, doing the same thing we'd done the week before, and the results were so different that we actually thought we'd done something wrong, either misunderstanding a huge swathe of the rules or at least in converting the characters. And then we checked and analysed, and discovered that we hadn't made any significant errors, the game was just giving us wildly different results even when we played it the way we had 2e.
Our experience didn't match yours, clearly.
As soon as we started, it was obvious that a direct conversion wouldn't make sense. So, using the conversion guide, we made choices that did.
For example, I had a Rgr/Dru/M-U. As a straitght conversion, he'd have far too many levels in 3Ed. I looked at the totality of the PC's history, concentrating on the most recent levels. How did he play? What were his most commonly used abilities?
Well, even though he had Ranger in his build, he actually wasn't the best melee combatant because of bad rolls. It was as if my dice hated him. But he had a nifty array of spells at his disposal, of which he used a very tightly focused subset all the time.
In the end, I dropped most of his Ranger levels and preserved his ability to cast his iconic spells- at least those that existed in 3Ed (some never got re-done)- and he became a Ranger/Druid/Specialist Mage: Transmuter with a big level disparity (and thus, XP penalty) between Rgr and everything else.
Since Druid became his primary source of BAB, he remained a less effective melee combatant than other warriors in the party...but he could still track & had Favored Enemies. And he could still cast every last spell he used (that existed in 3Ed) that mattered to the history of the character & campaign.
Some play going forward changed a little, but it changed in the same way for all the PCs. Which was expected, since there were key differences in the systems: feats, standardized stat bonus math, no level limits by race, etc.
Across the campaign, there was no need to retcon the campaign to account for how Event A, B or C went down, because most of those key abilities for each PC were still present on the sheet of the PC in question. The same PCs could still have taken the same actions they did in the 1Ed or 2Ed eras of the game.
Converting to 4Ed was comparatively nigh impossible.
Where the 3Ed version of the was now essentially a Druid/Specialist Mage dabbling in Ranger, the 4Ed version was...what?
Druids & Transmuters didn't exist. Key spells were gone. And by virtue of the design change, dabbling in a second class was as good as you could do- no 3rd classes, ever. Any significant improvement in your second class required the burning of Feats AND exchanging access to abilities from the core class to the one you dabbled in. Not eschewing advancement like in 3Ed, but actually unlearning some stuff. The breadth of ability the PC had via his spell selection was hyper-compressed into a wedge of a few, combat-only spells.*
Now, over the years, 4Ed added things like Hybrids that alleviated some of those issues, but it never actually erased them.
* there were spells that disappeared in the prior conversion, mostly ones from certain exotic supplements he rarely cast. But in the 4Ed attempt, he would have lost mainstream, run-of-the mill PHB stuff. To put it differently: 3Ed took away his Lobster Thermidor, 4Ed took away his hamburger & fries.
