Hi hi~ I don't think you could compare Fiesta to WoW.. I haven't played it, so I can't help you make a comparison, but I heard these two games are really different xD
Anyway.. defense (the END stat) is pretty useful for clerics because:
1. They draw a lot of aggro when they heal people.
2. They draw a lot of aggro when they heal people.
3. They draw a lot of aggro when they heal people.
I didn't copy and paste that LOL. If you want to be a "support" cleric, it's best to have END in your stats so you can "tank" when you need to (usually it's inevitable). It's hard for a party to survive if their clerics die really fast. But, you'll have really sucky damage and you won't be able to efficiently solo at higher levels so you'll definitely rely on a party/levelling partner.
But if you wanna be a "solo" cleric.. full STR is the way to go.
I think builds relate to how you want to play more than "which is better". I'm not sure how full STR is with a full support role; I'm sure they can support too, but I don't think they can support as well as END/SPR clerics unless they're stocked up with cash shop items (then again, you can do anything once you're stocked up with them, haha).
I don't know much about the 3rd classes so I won't comment on them and leave that for someone else xD.
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