I don't see why Bard or other "lesser spellcasters" should have highest-level spells like primary spellcasters. It's not like everyone with improving to-Hit chance can take specialization like Fighter. But it's only a part of the problem.
Another part is whether our obeisance to the ill-defined idea of “balance” requires to compare characters of
the same level or
the same XP total. The former doesn't make much sense, the latter runs into the fact that in AD&D2 Individual XP award are a thing, thus XP sums in one party will not be the same, and even the sign the disparity for the specific party
will strongly depend on the campaign.
Of course, Bard class
does have problems specific to it. Bard class in *D&D in general (on High Concept level) is built around a mix of capabilities that are either:
- Stealthy.
- Showy, i.e. the opposite of stealthy.
Obviously, these subsets don't mix well. Also, the stealthy subset is necessarily inferior to that of the purely stealth based class.
Looking at the context, in AD&D1 it was introduced as a prestige class for rather high level and already dual-classed characters. AD&D2 version is a simplification of this.
Considering 2 points above, if it looks a bit broken, and it's not clear how to fix it without breaking in an overpowered way (within framework of AD&D2), this should not be a surprise.
Another view of the problem is: Bard and all other "lesser spellcasters" (as well as
Hammer Horror Cleric) are
ersatz-multiclasses. As such, they were needed in AD&D1-2 at all only due to multiclassing being too clunky. And as an atavism of a hundred Exxtra Kustom classes with their little Exxtra Kustom spell lists in an older edition that didn't have multiclassing at all.
But in
this context, the first question necessarily is: if “Bard” class as presented is
de facto an implicit Thief/dabbling-Wizard(Song)/pure-Bard multiclass, what would purified dabbling-Wizard (<thaumaturgy school>) and pure-Bard classes look like? To the laboratory!