WHM doesn't really have a selling point anymore as its gameplay is essentially just "baby's first healer" and it offers nothing than all 3 of the other healers don't have a better version of. I know this sounds very melodramatic, but I'm really not kidding. Every tool they have, someone else has something similar and better except for Cure III, a high-potency AoE heal on the GCD. The radius of the heal is smaller than your typical AoE heals, so its harder to use and chews through your MP like it's no one's business. Their other main gameplay mechanic is that they grow lilies automatically while in combat--1 grows every 30 seconds to a maximum of 3. These can be used to cast Afflatus Solace or Afflatus Rapture, 2 GCD healing spells that are basically 0 MP cost Cure II and Medica (Basically Benefic II and Helios if you're not familiar with WHM's spell names). Casting these lily heals 3 times nourishes the blood lily which can be spent on a GCD spell called Afflatus Misery which partially refunds the damage you lost while you were forced to heal instead. WHM suffers from poor MP management right now and actually also has the lowest healing output because of their overall lack of OGCD healing abilities. Every other healer has twice as many OGCD heals if not more over WHM.

SGE on the other hand has the identity of a healer that heals through DPS. If you've ever tried Dancer, Sage has an ability callled "Kardia" that works like dance partner, only it heals your target any time you cast an offensive GCD spell. You can pass this around the party for optimal use, but your tank is obviously your prime target most of the time. The healing per cast is small, but adds up significantly over the course of the fight and takes care of boss autos for you, as well as topping off after tankbusters. They play similarly to SCH in some ways but without the faerie. Your main healing tools are your Addersgall heals: Druochole, Kerachole, Ixochole, and Taurochole. They consume 1 Addersgall of which you automatically generate every 20 seconds and can store up to 3 of. Using them also restores your MP. Unique to Sage is an ability called Eukrasia which is a 1 second GCD augmenting ability that changes your nuke into your DoT and changes your 2 GCD heals into barrier heals (similar to SCH's Adloquium and Succor), but you'll very rarely need the heals, if ever, as your OGCD healing library is very wide. SGE's biggest weakness is they can't burst heal that easily despite having the highest healing output overall, so it might seem a little scary when the party or tank drops low until you get more familiar with the job.