The first time I got hit with it was my 7th level fighter and a 9th level fighter. I failed my saves and died, but the 9th level fighter defeated them. The second time was my 7th level figher, a 9th level fighter, a 6th level figher and a 6th level cleric. That time I made my save and we all survived that encounter. (but the 9th level fighter and I both were killed in a later encounter. the cleric was invisible and survived that encounter and saved the 6th level fighter too. Having seen how the two stage spawn in the later area works, I'm sure that group can handle it now, but it still will be a tough fight.)
My issue is not so much with the overall difficulty as with the death magic. There aren't very many buffs against death magic available for single digit characters and even if you can reduce your chances of death down to 1 in 10 through bless, aid, etc you still will pick up dts from that situation if you keep facing it over time.
I think I'm probably pushing things a bit taking a 7th level character into the redlight, but I haven't many areas where the risk versus reward is any better at 7th level. For now I am mostly just steering clear of areas where I know these shaman hang out.
Upgrading the kobolds in the cave in the sielwood forest to something more like what the tougher redlight goblin once were might make a good intermediate challenge. Also the kobolds and kenkus near hlint would be good training for the 6-8 level crowd if they were upgraded by about 2 in CR.
Please don't mistake this for a complaint. I know you guys are really busy trying to make all the version changes and tweak balance and get a new storyline going and all those other things going on in the background. I'm just giving my 2 coppers on how I think things might be tweaked to support small parties of single digit characters adventuring for fun and profit.