Priests
In 2nd edition AD&D, priests are based on the crusaders (of history, not the kit). They are decent fighters and decent spellcasters. Compared to a, say, thief, they rocked. Skills and powers, plus Spells and Magic, made the problem worse. A lot of clerics had so many points they didn't know what to do with them all. An example is the crusader kit, which is almost as good as a paladin, but with full priest spells and none of the paladin's restrictions.
With Glaive, we decided that the traditional priest was more the home body, not the warrior. Priestly spells are the main stock in trade. Those priests who wish to be both devout and combative are best taking some fighter abilities.
Rogues
Thieves in 2nd edition AD&D are poor combatants, relying mostly on their thief skills. However, they tend to be in combat almost as much as the fighters. As a result, we have allowed rogues to have better thief abilities or combat abilities by decreasing the cost of thief abilities. Thus a thief could be the master thief who doesn't fight at all, or your more typical ADnD thief, who also fights.
Bards work well, since they can now really be a jack-of-all-trades, master of none. Glaive allows for the norse skald, who doesn't know spells, to exist. The bard's player simply has to choose warrior abilities instead of spell casting.
Mages
We considered a mages main skill to be spells. Other abilties included researching and school selection. Not all mages will have enough knowledge to research or know all schools, instead they speak their spells by rote. In such situations, the mage may have come from a primitive culture, and possibly know other skills as well (having thus spent some points on other classes).
Glenn Butcher / knight