A level 50 scholar in i70 gear does not have 5.1k health. Either you're using the site wrong, or the site is inaccurate. I know this because I have an alt with a scholar decked in i111 gear with 5.1k health.
https://imgur.com/a/lI0Vzop
I have also helped many new people through ARR, guiding them to do their class quest and equipping their i90 class gear after which healers are closer to 3.5k health than 5k health.
Posts like these just spread misinformation.
That being said it's not a huge issue because the echo sees people through after a couple of wipes.
I think if they were that low on health they may have not realised their last class quest gear is given as a coffer in inventory : ( If I went through on an alt equipping only my class quest gear and the accessories provided to me, my WHM should be around 3.6k. So they probably didn't realise, poor guys : (