I had my Rowanna tank the last lich like a boss while this was going on.
I dont think Rowanna would be able to stay alive without Savior buff.
Correct me if I'm wrong, but if Rowanna is solo tanking lich, savior buff would have no impact on her survivability. Savior gives only ATK and DEF, but no MR.
Luckily i had Sophie, she tanks them all with 30MR <3. A true sadist xD