a) Since they're singing the Chant non-stop 24/7 in Val Royeaux, they can easily do it in full, yeah :) But from what we've seen and heard around Ferelden I understood that it is supposed to be recited in every chantry, as much of it and as often as possible. If the little village chantries manage it, what's wrong with the Kirkwall cathedral?
They can be as political as they want (although I wouldn't say that Elthina is... unfortunately for the city :E), how is that stopping them from performing one their main functions?

b) True, Varric can be used to handwave everything :D