Thanks!
The removal options are
Vapor Snag,
Spatial Contortion, and
Dismember. However, having
Path to Exile fulfills the need for removal pretty well. Most merfolk decks I've played have had between 2 and 6 removal spells, and Path is by far better than the other three.
The
counterspell options are a little better;
Spell Pierce,
Spell Snare,
Remand,
Mana Leak, and
Disrupting Shoal are all potentials (Mostly Snare and Shoal and Pierce) but they are all pretty bad with Thalia, which makes me hesitant. It's possible some number of Shoal is correct even though Path and Thalia are white. It's also possible Snare is just better in that slot due to the white cards, and
Spell Pierce is definitely good right now even though Thalia makes it cost 1 more. Soft counterspells even work well with Thalia.
I like 8 LD-ish effects for a couple of reasons. 1) Tron and Eldrazi are a couple of the biggest decks right now, and they're great vs them. 2) Jund and Abzan are both big decks, and they have a hard time dealing with color screw. 3) They get better in multiples, so 10 is much better than 6 (I'm counting
ghost quarter) 4) They're rarely
dead, just sometimes bad. Killing manlands is good because most decks play them, and even against blue decks you can often cut them off a color, especially if you have 2 or a
Ghost Quarter.