Isn't this new content suppose to be for the solo player? If they make the bosses require grouping then they will kill the zone and upset a lot of solo players that have been waiting for this DLC release. The only work around I can see is make the bosses scale to your level and not be zone level. I know this is an MMO but there is a player base that can't stay online 24/7 to level and they generally don't have others to run with. The new grouping tool MAY help this but hard to say. I would hate to see them make another Craglorn out of this content.
I have yet to to get any of the ones I found bellow 60-75% solo.It will take me some more tries and gearing to get them down but probably can be done..I don't have the best gear though. Magicka NB still in MK with ~300Cp.
I think they should be soloable and their difficulty is pretty great for a solo fight at this point. I would not want them buffed to a level requiring groups. I wouldn't even bother with them if they buff them to the point of requiring a full group.
The only problem I have with them is that they will probably be zerged constantly when the DLC launches so the opportunity to have an awesome solo fight will be pretty rare. Have fun with them on the pts for now.