You make it sound like all bards lost some ability because they can't use all bard masterys at once, and they haven't. Bards have the same abilities now that they had before, but you can choose to have two more special abilities.
Pretty much you have to plan ahead whichever character you are playing, not just bards. Do you have the right slayer? All of my equipment repaired and going to last through the night? Do I have a charged bag of sending? I look at all of these with every character when I go out for more than a quick walk through.
Sure, I agree that the quests are silly (stupid even) and monotonous. But my bard is far from useless.
Every character class has to do the things you mentioned, bards are no different in that sense. But bards are the only ones that need to perform anything like a quest to switch skills. Archers don't need to go kill 10 mongbats to figure out how to switch from using a bow to a crossbow. Mages don't need to slay 5 cows to figure out how to cast mysticism or necromancy spells after using magery spells for a while (assuming they have those skill points). It's not just the requirement of doing a quest, but also that the skill points dedicated to these skills are less effective because they cannot be utilized.
No bards didn't lose anything with the addition of these masteries, but that's not the main issue underlying bard complaints. The fact is that since bards last got any attention (the addition of discord along with a HUGE nerf to provoke), every other class has gained incredible powers while bards have remained static.
This has been covered so many times already, but compared to how things were:
1) Archers & warriors now benefit from 180+ stamina, 50+ swing speed bonuses, stamina & mana leeching, bushdio specials, chivalry specials, weapons specials, loads of beneficial arties, imbuing (something else that benefitted everyone but bards). Compared to a 100 dexterity archer/warrior of the past, a sampire or ABC archer can do 20x (not an exaggeration with 250 point hits and insane swing rates) more damage over a given period of time.
2) Mages now benefit from 200+ mana pools, 20+ Mana regen, LMC, LRC, FC, FCR, entire new schools of magic that can be combined to even greater power, mana leeching for non-stop spellcasting. Harken back to the last time bards received changes, and Mages could cast 3 maybe 4 7th circle spells before needing to stop to meditate. Now, they can cast faster, with less mana, and leech more than they can ever use; to say nothing of huge damage from slayers and SDI (bards to not get additional damage from slayers, nor do they benefit from DI or SDI). All while bards have received nothing.
3) Tamers have pet bonding, not to mention a new set of pets every publish, from Greater Dragons & Dread Warhorses to rune beetles, raptors, bake kitsunes. And the key benefit of pet bonding is that tamers can always have a fully trained pet at their side. So, let's just estimate that a fully trained pet is about 5x more useful than a fresh tame, and a GD is at least 5x better than a normal dragon. 25x more powerful? At least.
Bards never benefited from any improvements in swing speed, casting speed, huge pools of stamina & mana, elite artifact equipment, imbued equipment. None of it. So now that bards finally get something, why is it so severely limited?
A sampire can benefit from a necromancy spell, along with chivalry spells, and at the same time use bushido spells, not to mention shield-free parry bonuses and weapons specials (tactics). They can master 6-7 different skills and employ them all fully all at the same time. But a bard cannot master more than one bard skill? What a load of cr@p.