5. Depending on how comfortable you are with only one "healer" and what the mob composition is, I'd give the last slot to:5a. If another "healer" is needed... a E.Renewal PS/SB/Infuse/Shield Guardian/GDW build (or its weaker hero equivalent).
5b. If casters are a problem beyond what the AP-MoP necro can handle with Technobabble... a broadhead/volley ranger.
5c. If neither of those are concerns... a MS-DB sin. While the rest of your post was okay enough that I don't feel the desire to go over it right now (and actually you inadvertently caught one of my blunders: I left out the bar variations for the bitch bars, and only posted the Hero variants, which is why there is a complete lack of GDW here. I will get around to fixing that problem tomorrow, or so, when I can think entirely straight again), I'm going to directly dispute this bit here.
5a. The only time you should need another healer is for DoA (or 12 man elite missions, but those are clearly the exception to various rules). I have run the Solo AP Boon in every other PvE location with great success. If another healer is needed, the AP Booner is probably doing it wrong. Practice makes perfect though!
5b. Casters are useless when they are either knocklocked or dead in a few seconds. Extending their cast time is nice and all, but generally entirely unnecessary. I personally consider dropping sheer killing power for unnecessary utility a negative change. However, adaptation of the builds to individual needs or play styles is part of the GW process, so everyone is entirely free to bring whatever they want. So on that note, I will also slip some variation stuff into there when I can do so properly.
5c. Well... Yeah. MSDB or a Dwayna usually got it with us, and still does with my own various groups. More melee is cool. :3 Quote:

The AP monk, for one, looks like fun.