As a general rule, Barspells are essential in specific endgame fights (flight-capable wyrms come to mind) and are relatively unimportant for day to day concerns. It really depends on what you do. If you don't *do* anything, like wyrms, that depends heavily on Barspells (and no, I'm not just talking about Barfira to minimize casualties from Mijin Gakure), then you may well be better suited with some other merits instead (Regen's the usual choice, a few like Divine Seal recast). If you *do* do stuff that depends heavily on Barspells, you will naturally want to merit them.
Simple (or not) as that, really. It's a situational thing that's awesome if you have cause to use it and pointless if you don't.
Alternatively, put off the decision and merit some other stuff.
Group 2, at least, is somewhat more straightforward. Shellra 5 is awesome and should be fully merited, Devotion should at least be unlocked, Protectra 5 is nigh on useless (very pretty, but it's not worth meriting something for 5 more loldefense over Protectra 4, all the way up to *9* more loldefense if fully merited), and Martyr is up for debate (it's instant and costs no MP directly, but that's about all in its favor).