So on your advice, I'm investing the feathers to 5* my +spd/-res Tharja, and every build I see for her includes Moonbow.
Of course, I have piles of this useless piece of s*$% oaf dumbass Odin, but only one 4* of him. So while I'm prepping him for the oven, I notice he also has R Tomebreaker 3.
So I see Swordbreaker on more than one of her builds, but I'm tempted to take the Tomebreaker as well... I suppose with the double xp/sp event going I could grind her to get whatever SP I need. But I would still inherit Swordbreaker onto her as well; I assume I would swap between the two as needed.
But is it really worth investing the time to have more than one breaker skill?