Trying to balance the entire game off of the most optimized single-dimensional character builds only makes well-rounded characters no longer viable.
Well, another problem: Remember Stalker0's analysis of skill challenges and the errata of the skill tables (pg. 42)?
Well, with additional stacking bonuses, the spread between specialised and non-trained characters becomes even more pronounced.
A non-trained character has +1/2 level + ability mod.
A trained character has +1/2 level + ability mod + 5.
A skill focused character has +1/2 level + ability mod +8.
With the right background, a focused character has +1/2 level + ability mod +11.
Assuming that a specialised character has also a higher relevant ability score, there's easily an additional +2 to +4 in there (compared to the non-trained character) - for a total difference of +13 - +15.
On a d20... that's a huge difference. The spread between trained and non-trained characters in 4E was minimised by introducing the flat +5 for trained and +3 for skill focus. Every new bonus draws us closer to the situation we had in 3E - that trained characters either auto-win or non-trained auto-lose.
The design tenet of 4E was, however, that everybody should be able to have a shot at it, otherwise you have the trained character playing, the others waiting.
The additional skill bonuses are getting us closer to exactly that.
Cheers, LT.