You are right on what those splashes give. But then the natural question is: why not multiclass then? It is an option open to all classes. Why not use it if it is so good? Moreover, why should the 20 levels of a single class be equal to the benefit of splashing?? Sure, Bard 20 should get also +30 saves, +1000 spell points, +700% damage, ranged aoe instadeath spell, and instant quest completion button.
Funny that "Rather than focusing on nerfing multi-classing, you should consider boosting the capstone" line
D Dialectics, implied premise recourse: "After stealing the money, did you spend it?" asked to someone who did not steal it.
Again, multiclass is not the cause of any imbalance, it is precisely (!!) multiclassing that brings balance to the classes, to the game. It actually creates character balance (!!). Also this are the core rules of this game. Multiclass options have already always been taken into account for DnD and DDO game construction. Always. No, it is not the "it has always been like this" argument, it is the "we play basketball and the ball is spherical, not squared, and it is a core rule which won't change" argument. You have n heroic levels, and you can take levels from max 3 classes. Choose wisely. Plan ahead.
The thread should have been named maybe "character and playstyle balance". I applaud the synthesis and the conclusions given by the devs on all the discussion. I feel they are listening very carefully and making a monumental effort in building and developing this deep, vast, complex, multidimensional and incredibly entertaining world of DDO.