I think the primary major shortcoming of the Paladin and Sorcerer is the lack of the Druid/Knight duo synergy.
Imo the difference is huge in effort of going to exp if you just need 1 hunting partner to duo hunt, instead of usually 3 for a full team. The duo hunting also offers more spawns since a full team clears faster and therefor might overkill a spawn. But the duo might not overkill.
Sorcerer: The major shortcoming of the Sorcerer isn't the sorcerer itself. The shortcoming of the Sorcerer is the druid. The druid is almost equally strong, while still ALSO having the huuuuge roll as a healer. The druid's ability of Paralyzing in PVP also creates a huge gap between themselves and the Sorcerers.
The Sorcerer's lack of "Cure"-spells is not a huge drawback, but it might be really significant and people often seem to neglect that problem. In pvp it is really noticable imo not being able to Exana Flam if you're soulfired. In PVE the other vocations that have more "Cure"-spells than just Exana Pox that the Sorcerer has, they get an ability to escape with teleport scrolls or The Supreme Cube. This because they can kill of the mobs, use Exana Flam or Exana Kor etc. and quickly hide in a corner and wait battle, while the sorcerer cannot.
Druid: More waste doing bosses, if waste isn't split between the teammates (which it almost never is with randoms and mostly not even with premades). The higher pressure and intensivity of having two vital roles both as a shooter and a healer. Ofc good Sorcerers and Paladins can help out by making pulls, taking mobs and secondary tanking and more, but the druid still has two primary rolls. The druid lacks the Sorcerer's death protection equipment, which can be very useful againt current bosses that often deals death damage and by player's SDs in PVP.
Knight: The pressure on the knight during lots of different bosses is to have the responsibility for boss mechanics. For example. trapping bosses at certain tricky places, luring them over certain squaremeters and so on, while still focusing on tanking it, both using Exeta Res, healing yourself and still attacking it with your spell rotation. Boring not having Creature Illusion. Can't summon creatures (except for your lvl200 vocation specific summon). Impractical not having Invisibility spell.
Paladin: "Jack of all trades, master of none" in general, but really shines through on lower levels. Having lower HP than knights while hunting, killing bosses etc. Of what I have seen while doing some of the higher level bosses is that paladin's are the most likely getting headshottet and dying (personal experience). Boring not having Creature Illusion. Can't summon creatures (except for your lvl200 vocation specific summon). Impractical not having Invisibility spell.
These are both big and small factors and I see most of the vocation specific shortcomings by putting the vocations in contrast to the each other. There's probably lots of other shortcomings but these are my experiences.