Mass Aid is a level 3 spell (it can be found in Spell Compendium page 8) and the base (non-mass) spell Aid is a level 2 spell. This is just a +1 difference.
All other Mass spells have about +4 levels to basic versions, not +1. For example, cure light wounds is level 1 and the mass version is level 5, same with moderate serious and critical cures, and they all have a limit 1 target per lvl too.
Mass Aid also does not have a limitation of one target per caster level (RAW) like most other spells.
One could say Aid is [single target] Bless plus a preemptive Cure Light Wounds. Aid is also comparable to False Life, a lvl 2 mage spell. I think the extra hitpoints of Aid is a lot more important than the paltry bonuses of Bless at low levels (when some characters have really low hitpoints and can't survive even a few AoE damage). But still compared to Mass Cure Light Wounds, Mass Aid seems way underleveled.
Is there a reason it's so wacky?
Am I missing something?