Wait, I think I have it somewhere.... Ah, yes:
[W] 35-155 (+20%AP) 1.5s // 10s CD // heals by 30-110 (+20%AP) up to x1.5 based on missing hp
[W] 60-220 (+40%AP) 4s // 22-16s CD // makes allies travel large distances
[W] 80-180 (+35%AP) 3s // 14-10s CD // throwing animation (3s) refreshes shields.
[E] 80-200 (+50%AP) 4s // 10-8s CD// +40-60%MS for 1.5s
[E] 80-240 (+40%AP) // 9s CD // 10-30 flat resistances
[E] 80-240 (+60%AP) 6s // 10s CD // adds 9-105 (+15%AP) damage to every attack
[E] 80-240 (+70%AP) 5s // 10s CD // +14-50 (+10%AP) AD to target
[E] 70-350 (+70%AP) MAGIC DAMAGE 5s // 23-15s CD // Immune to CC
[RE] 110-410 (+80%AP) 4s // 45-36s CD // half to surrounding Allies // +60%MS for 1.5s
Karma had the same base values as Lulu and Janna until 5.10 They lowered the scaling values for the shield (lvl2-5) but also decreased the cooldown, to emphasize the mobility impact.
Currently, Karma compares better to Lux and Orianna's shield, but is the only one who can instantly apply it. She even has the strongest shield at 400+AP with the lowest CD, even though Lux can possibly shield for twice the listed amount, and more targets, if aimed well. In exchange she has a cast time, it's a skillshot and it protects from the least burst damage.
Either way, Karma's shield values don't seem unreasonable to me.