If you really played a healer on Ragnarok Online, then you'd know you have only ONE attack spell and that was unlocked via a quest. Otherwise, you spammed Lex Aeterna, which was a debuff that made the next attack do double damage; that's hardly the same as attacking and doing damage. You only got that if you went down a certain path in your skill tree, too. If you were a solo player leveling up a priest, you basically had to heal-bomb undead to level up. Otherwise, you'd have to build a healer that used physical attacks, which cut into your use as a healer (because a priest in WoE was most effective healing teammates and using one of the two things that'd heal a castle's crystal).
Since you mentioned Neverwinter, which is on Perfect World's arc launcher...
Forsaken World's blood tree Vampire has a buff that literally turns off the ability to attack and adds some nice buffs to your heals (like activating instantly, adding attack buffs to your heals, increased potencies, reducing heal cooldowns, etc.). A divine priest in the same game was most valuable healing and sometimes MP draining with a skill that could be used only so often.
Perfect World International, before 5APS broke the game, high-end bosses simply hit too hard to do any kind of attacking or used a ton of AoEs, or both.
From what I recall in TERA, there were tons of times a healer was kept busy, wasn't safe to attack, kiting mobs, etc to afford very little chances to attack. Maybe that changed after I stopped playing (which was when FFXIV had their third closed beta). Not to mention the damage from a healer was laughable compared to DPS classes (Berserker hitting 1m+ in damage). I know mystic had a really strong summon that lasted for a stupidly short amount of time, but otherwise, you dropped motes and had a much weaker burst heal compared to a priest.
Basically, some of the older games rewarded healing and tanking more than healing sparingly and aggro-generation sparingly. FFXIV is really the only game I've come across that has such a high impact of tanks and healers doing damage.