I call BS.
1) Challenging does not immediately equate to "more healing" and "more healing" does not equate to "challenging." Many of the Stormblood encounters have some stupid mechanic that drops your HP to 1 forces you to heal up and may even throw in a doom effect if you don't top people off fast enough. That is NOT challenging. It's not even much fun Spam 2-3 AoE heals and you and your partner got it down. Heck a WHM can do all the healing by themselves if needed.
2) Time limits. You will still have time limits on trials and boss fights in raids. More healing = less damage = taking more time to complete. If there is so much healing going on, you're going to see a lot more people having trouble getting past the time limit which means they are going to be even more picky about what DPS contribution they can bring to the table. Sure, maybe tank and DPS damage is going up. But why can't healers contribute something even if it's just a buff why do we get 1 DoT and 1 Direct Damage spell in our whole kit and enough heals to smother us?
3) Speaking of dungeons and time... I'm willing to bet there's going to be a HUGE stink once people get to end of content and are farming tomestones only to find that it takes significantly longer to go through a dungeon because the healers have to heal so much and can't DPS like they used to. Tanks not being able to pull wall to wall? I can hear the screams of the speed runners now. DPS queue times going up not because there are not tanks or healers but simply because it's tanking longer to complete each dungeon. Personally, I wouldn't mind that. But I know several people on some of the other servers I have been on that would just agonize over taking even 1-2 minutes more. HELL wasn't that one of the reasons people complained about Stoneskin? F-that I don't wanna wait 3 seconds for stoneskin. Hell they're even saying that about Protect.
4) Why can't healers have more engaging mechanics to heal with? DPS and tanks have their combos. RDM has an awesome system of their black and white mana... healers have... well... yeah... AST cards were a lot of fun. Make AST heals HoTs or time-release heals to let them have the time to manage their cards while the healing is taking effect, and you've got something far more engaging than the hogwash they spat out in 5.0. I'll be honest that I'm not sure what they could do to scholar and the fairy-- I was never fond of the pet for healing so I can't think of any nice ways it could be used... but maybe something like they did with the summoners? The whm lilies being automatic now are just... meh^3. They were always meh and always will be meh. WHM needs a fun and engaging mechanic and they need to stop feeding it skills they took away because they can't be bothered to come up with unique skills and abilities for it. There were a crapload of suggestions in the Ye Olde Thread of Salty White Mages(R)(TM) back in 4.0 and in 5.0 we ended up getting 3 different themed games of an electric Simon Says game.