IMO that's the perfect numbers for progression. Of course, raids progressing today have 10-15 ilvl more than we had, so most of the 3-heal fights can also be done with 2 healers, but it doesn't really make them easier. We used exactly those healer numbers for progression, but we found Thok easier with 2 tanks than with only one. Can still be done without fire phase (if you go for high stacks, which you should with 3 healers) and you get less random tank deaths.