I think both Plasma Bolt and Tidal Pulse will both feel much better if, as noted elsewhere, the global cooldown is taken out, as it stands I am losing considerable DPS on both because of it.
Plasma bolt is "free" already but as to Tidal Pulse, personally i'd say the problem it has is that if i want piercing then i'm going to take the high damage ones, and compared to the non-piercing spells it is expensive.
It does need the extra hook to it, maybe make it hang around for X seconds after it has reached a certain distance, creating pools of water if you will. That way it has become more distinct and it's not really competing with either the piercing or non-piercing spells. It would probably need it's damage decreased a fair bit.
EDIT:
On the topic of DPS, MPS what have you, maybe they should be toggles in the options somewhere, so 1) you can pick which ones you want, and 2) People who don't want any aren't bogged down by the info. This way you could also add tooltips to explain what they all mean.