Tydeus, you are comparing a specialist build to another, very extreme specialist build rather than a hybrid build to a pure build. It was the latter comparison that I was trying to make in my post above, which, as I explained to you earlier, was unintentionally ambiguous in certain areas. I have since corrected some of those ambiguities to more accurately reflect what I was trying to say.
In any case, what I feel a more appropriate example would be for weighing the merits of a generalist hybrid vs. pure specialist would be:
Level 30 (4 420 577 xp)
Strength: 18
Agility: 18
Skills to attributes: 2
Ironflesh: 6
Power Strike: 6
Shield: 5
Athletics: 6
Weapon Master: 6
One Handed: 118
Polearm: 119
compared to
Level 30 (4 420 577 xp)
Strength: 18
Agility: 21
Skills to attributes: 8
Ironflesh: 3
Power Strike: 6
Athletics: 7
Weapon Master: 7
Polearm: 165
The generalist build is a lower level variation of the build I use on my main, and one that I've personally tried on an STF. It gives you good protection against ranged fire, cavalry, and teamhits--adaptability in other words--in exchange for average damage, speed, and swing speed. Basically, it has the ability to respond to many different situations but not the ability to respond outstandingly. In spite of this, it is a very excellent build. The fact that it does not have any major weaknesses is its greatest strength.
The specialist build, on the other hand, is very powerful for a level 30 build. The extra ~50 weapon proficiency basically translates to another level of power strike over the generalist build, on top of a gain in swing speed that is further augmented by the additional rank in athletics over the generalist build. For someone who favors flank attacks and usually goes for big plays, it is undoubtedly the better build. The benefits of investing in a hybrid option like riding, shield, or 1h do not outweigh the drawback of taking away stats and skills from the primary role of the hypothetical hero that would choose to specialize in this way.
It doesn't seem to me like there's a lack of parity in terms of effectiveness here. Both hybrids and pure builds are equally viable, despite focusing on different things.