Doppelblade is one of the ones i shattered because i never used it.
Armor Strike is a garbage ability that i shattered long ago. You should be using Guardbringer with Gaia Cross ideally, or Saint Cross is what I used before Guardbringer came out. Retaliate is also great on characters that can use both obviously.
You also don't need that much DEF stacking for Guardbringer. Protectga, Wall, and Gaia Cross alone will get Guardbringer to 4 hits.
Also in regards to r4, you shouldn't need to go that high. Two r3 abilities is 12 uses total, if you go over that you're losing medals for Actions Taken and should probably adjust your strategy.
Taking abilities to r5 is especially unnecessary (except for summons). I also alternate between Full Break and a breakdown for dps without worrying about timing, and my FB is only r3 and my breakdowns are only r4.
Balphon seconded you, and as I was forming that list, Doppelblade was one I figured I probably could shatter, currently though it does about 12k on a couple characters who don't have better at disposal. Like Edge, I sometimes use it with him.
As for ArmorStrike, why would you call it a garbage ability when I constantly do 8k on a boss before buffs/debuffs and 9999 with any kind of buff? I mean, when you used it, did you ever see its potential?
As for Guardbringer, that's much more costly and it's a 5star at rank 2. Also, I don't remember, does that one have a holy element? Probably not, but regardless, while not hard to get those 4 hits, again mine is only 4 uses, and Armor Strike is a sure 9999. Great for a long fight or a torment.
As for Saints cross, ya, I love that ability. The only times I don't use Gaia Cross with Armor Strike or Saints Cross with Banishing strike, is if the elements associated with them are not ideal.
To recap! I'm thinking I may shatter doppel, but I used it just this last raid on Edge. He had doppel and shadowsteel or whatever it is, with Ninja abilities doing much more damage, doppel hit for 6k-6500 x2, and shadow hit for 8500-9999. This was without Shout or History's Truth or any 610 buff.
I think Armor Strike is a good ability.
Edit: As an aside, if I ever don't get all medals, its the usual 1 for actions 2 for damage taken but still an overall master that I see is pretty common. I don't always use up all my abilities either, but the Torments really make me grateful for this.
Someone posted something about a Torment being easy one time, and Syntsui or however you spell it quickly posted "hones". Obviously meaning a new player wouldnt have the hones necessary.
Ultra Cure is rank 4, but the only times I dont use it up is if I'm using a burst heal like Relm or Eiko. If I'm not using a burst healer, I have to slot in Curaja with 12 hones instead.