nutaku doesnt have serial codes for aigis, while DMM mainly gives serial codes through purchase of their goods (like Aigis character profile, Aigis LN vol. 1-4, and the more recent sybilla nendoroid preorder. There are also some other serial codes from real life events in Japan)
and grats on clearing IB. just remember to use sybilla/clissa as lich tanks next time. Bernice isn't all that good as a lich tank.

as for healers and their healing speed, the main issue is the fact that regardless or how many healers you place, most of the time they will stack their heals (i.e. heal the same target at the same time) since they have the same healing speed, so unless the tank is able to last a couple of hits (usual 2~3 to be safe), having more healers doesnt actually help. what is needed are healers that heal at different rates (shaman during skill, bishop during skill). it's pretty rare for 3 healers to be unable to heal enough when placed together at a choke point.