Why does Sage punish you for using your healing spells?

[Sylve]

Apparently not, because I have to focus heal too often. I can't even attempt to use a damage ability or some of these tanks are probably going to die on some pulls. I have to be playing it wrong, like I have to be, but I am not sure how I can be.. I use their kit, but STILL I have these tanks drop so fast. Maybe these tanks aren't using cds, I, admittedly, haven't been paying attention to that when I am healing on it, but I don't know. Maybe it's just my anxiety talking, but I think I hate the class. Simple as that. I much prefer white mage.

100%, its the Tank not using their cooldowns.
In the first week after i hit 90 on Sage and did the EXR dungeons, many a tank came through in full 89 Job gear and i had to use every Addersgall charge, Rhiz, every oGCD button and was still needing to spam E-Diag to keep them off the floor. And then they sprint directly into the next pack to do it all over again! T_T
Recently dove back into SCH and was doing the 81 dungeon. Tank did a mass pull and died despite having Fey Union attached, SS, WD, spending every AF charge at my disposal AND bending every GCD to Adloq with every emergency cooldown blown.
And when he died, the Monk was easier to heal despite that no mobs had died yet, lol. Easier to the point i was able to Raise the tank and tap him back to full while also keeping the Monk alive >_>

And the the other night, i finally convinced a friend who was adamant she couldn't tank the 90 dungeons because her gear was garbage (She derped and forgot entirely about the job gear lol) to tank EXRoulette for me.
She went in on her DRK still wearing level 80 Crystarium armor with a couple of dungeon pieces between 83 and 87. How she even had the ilvl I'll never know but aside from needing to use E-Diag slightly more often than the average for a pull, i was still able to heal her easily enough and keep her HP near full for entire mass pulls while spending the majority of GCDs on Toxikon and Dyskrasia.

But shes a good tank who knows how to use her cooldowns. And thats the difference. Tanks mitigation is way more important now than it used to be. Partially due to the early stages of our ilvls but also because of the stat squish.

Panhaima+Kerachole+Pepsis II+Dyskrasia to open a mass pull. Your tank will be nigh impossible to kill due to the combined 100/130/170 basically equating to spamming Diagnosis on the tank while also doing AoE.
Gets even better when you add Soteria to boost Kardia's effect.
If the mobs are still alive after that runs dry, Taurchole for the DR and mixing E-Diags between dps GCDs so you dont waste cooldowns before the next pack.
Also, loading up Eukrasia and holding it while using Toxikon/Dyskrasia can help with reactively dropping E-Diags to smooth out any damage spikes the tank suffers (Many of the larger dungeon mobs have mini tank busters)

I have actually found Sage to be the Healer that clicked best with me. SCH, AST and WHM just feel awkward and slow to me now