As far as I know, there are three tiers for professions.
Tier 1: Fighter and hybrids (Lord, Valkyrie, Ranger, Ninja, Samurai, Monk)
Tier 2: Burglars (Rogue, Bard, Gadgeteer)
Tier 3: Casters (Bishop, Priest, Alchemist, Psionic, Mage)
A Rogue can easily make up for being tier 2 with Backstabbing, and it stacks with Berserk from the Bloodlust Sword, so you don't even notice his malus.
The Bard and Gadgeteer receive a serious malus from being tier 2. My Bard and Gadgeteer, at level 30, have Dexterity and Speed maxed, as well as Close Combat, Sword and Shield. The Gadgeteer, with no help from items, still only has 2 attacks per round, with the chance for 3 swings per attack (not guaranteed; thankfully, the monsters also have this random chance for 1-3 swings per attack).
The Bard has a bonus from her Oberon's Greaves (+10 Speed), as well as Mercucio's Blade (+15 Close Combat), so that barely puts her into the third attack per round, assuming white encumbrance.
This would mean that the casters in my MDP have a snowball's chance in hell at getting the third attack per round.