Thanks for this listing.
Well i agree but with 50 skill points a char is more suitable for veteran mode than typical for mercenary mode!?
Generally i think the hole game-balancing in DS2 gets a bit beyond of control anywhere around/above level 40.
As mentioned, playing a(ny) mage
within mercenary mode may be painful but towards veteran mode and above they get quite strong (if not the strongest char types at all) and in v2.2 even more.
About (summon) armor values in v2.3/BW: While GPG has rebalanced/reduced the magical armor bonuses they seem to have forgotten to apply these changes with pets and summons. I don't think pets/summons have been skipped here intentionally, at least partially this armor-balancing should have been applied on them too.
In the Aranna Legacy mod this already has been done for pets in order to get pet stats that are more resonable compared to chars and the same/similar should happen for summons too - so far this has nothing to do with multiple summons, this is rather some kind of game fix.
About balancing multiple summons, Ather Blast really must be revised. Perhaps it's also possible to add a new aggro-type making monsters angry directly on the caster if too many of his summons are nearby - this will surely bring the challenge back. Of course you still have a generous damage output but woe betide you if you don't use it or the related skills wisely.
...and soory for drifting away a bit from the main topic.
