Its been a while but;
1. Kill trash
2. Engage boss 1 (the one that pops books as a % of his health is reached, 75%, 50% etc.
3. MT stays on Boss, group burns books as they pop.
4. Kill trash
5. Engage boss 2.
6. Enchanter mezzes the books as they pop (these spawns are timed as opposed to % of health).The rest of group burn boss.
7. On death of boss, succour or deal with each book separately if no porter.
Obviously that’s a concise version. As for the strange things happening, it never happened to us but we do Skylance 3 quite often for the aug drop and every now and then a mob has popped randomly. My only guess is this is a bug and should be reported.
Cannot guess on why your chanter is getting summoned though. Maybe just don’t FD on 1st book.