If you don't have any plans on getting Water skills, you can ignore them. I've only gotten the Novice Mastery so I can learn Water skills (PVPer).
Of course, that means you can't use Water Elemental. Water Elemental only increases the skill's level if you have the Mastery learned. That would mean Rabana Mantle would be the only option and getting a level 9 or 10 opt may take time if you're unlucky.
You may find Purification to be an "ew" skill now but most Minstrels have it now due to (Expert) Coliseum practically being the only thing you do at level 170+. If there are two Minstrels in the party and the other has it, than that's fine.
The Parasensory path is mostly meant for power due to the passives the skills before it provide.
Leveling outside of Coliseum, Elemental Flow may be useful but doesn't mean you won't have to use the occasional pots. Inside of Coliseum, it's only good in the beginning at best (with a good party).
Spell Damage Power increase skill damage, which is good outside of Coliseum. Inside, not so much. The beginning is usually easy so you can cast ES. Once you reach the second half, the only skill you should be using is Guitar Group Heal and Fortissimo.
Parasensory just helps increase your AP to 200. You have to get the other 100 to be able to cast Performance of Harmony. Performance of Harmony is an important skill and if you don't have it, no one wants you in Coliseum.
I found getting 300 AP is easy since the big mob inside combined with ES is enough. My friend has it and he can buff us before we start while I use Energetic Performance.
I found the Crit tree utterly useless. I mean seriously, 9 skill points just for a lousy 3% Crit Rate? If you don't stack a crazy amount of Magic Crit Rate, you're just wasting points. :x
Don't get Bolstering Performance. With your spare points, you'll want to get either Holy Performance (Defense) or Energetic Performance (Damage). As I said above before (again /shot), people want Minstrels that have beneficial skills to make the run easier/faster.