Thanks for your feedback, Drake-Cid.
It seems as if most of your concerns are due to the numbers attached to the skills and not the actual skills themselves, which is most understandable.
I wanted Coral Barrier to be a useful skill and not something someone looked at and thought, "Meh, this can be skipped." But in so doing, I realize their is a fine line between making it overpowered and useless. This skill is designed to act like a redistribution of damage; for example, you receive 50% and they receive 50%. I agree that the numbers need to be tweaked, but to what extend, I am not sure. Considering she has no protection besides the barrier, I would like to make it somewhat akin to Oak's shield, but with obvious vulnerability and a bite to it (should an enemy demigod press the attack on her while the barrier is up). I could feasibly see the shield going from 25%, 40%, 55% and still be effective, but worry that many people would likely not want to invest in a 25% short duration damage shield and would bypass the skill altogether. Additionally, I'm also in agreement that the cooldown and duration of the skill may need to be increased/decreased (say 30s cooldown / 5 sec duration; I updated skill with this change in main post). I imagine the skills would be spread out, so that the best barrier would not be obtained until level 10 (or so). One thing to note though, is that any damage generated by the barrier can be mitigated by simply not attacking her while it's up. I've changed the skill to reflect autoattack damage, as there could be some issues with reflecting mine and tower damage. Lastly, the (heavy) mana cost of this skill would severely limit how often this skill can be used. If you have suggestions for better numbers, please feel free to supply them.
With regards to Osmosis, I think you may not be looking at the entire picture, as this skill has potential to be very useful. Because the siren is meant to be in melee combat, Osmosis is meant to keep her in combat for longer periods of time. Additionally, it is a skill that allows her to drain both health 'and mana', which no demigod currently does. Combined with Tidal Wave which negates regeneration, she can effectively drain away a enemies's health and mana while sustaining her own. The usefulness of this skill greatly increases as she levels due to the higher autoattack dps, which yields greater health and mana drained. Additionally +damage/+attack speed armor also enhances the effectiveness of this skill. Just with the purchase of one popular item, Narmoth's Ring, she can drain 20% health with her autoattacks when she has all skill points invested. If she were dealing 300 damage per second at level 15, she would be effectively draining 60 HP and 32 mana per second from an enemy, which is very useful, and likely an underestimation of what she would be capable of in melee at 15. If she were to get crit gear, the usefulness of the skill would dramatically increase. This is one of the skills that you really need to look at the big picture to see how useful the skill can be.
Yes, I understand that Siren's Call range is likely to be large when all skill points are invested; this is an issue with how do you balance a skill that does no damage but has great tactical use with range. As a side note, Regulus has the option to snipe across the map with tracking, negating his range limitation with respect to clouded areas at level 5 (most good Regulus players chose this option at 5 for obvious reasons). This is just one of the skills you'll have to look at think, would it be useful with a different range? If so, please provide a range you feel would be most appropriate. This could simply be fixed with negating the last level of the skill, and keeping max range at 45, which I still feel is very useful.
I didn't give thought to what her starting movement speed would be (but 6.0 sounds reasonable), but you bring up an excellent point. The reason I wanted to give her a movement speed increase was because of her lack of snare (beyond Siren's Call, which is short duration and on a long cooldown). This was also the reasoning why her movement speed increase was greater than what was granted by Inner Beast, because UB has access to a melee snare. You mentioned that no other demigod receives a bonus to dodge, and that is exactly why I want to implement it in this skill. Dodge is not a heavily used skill because it forces a demigod to sacrifice HP with regards to item choices, and really only becomes lucrative when you have a lot of it. I wanted to give her the option to be heavy in dodge, but frail with HP, if the user so chooses.
If waterwall doesn't allow passage of allies, it opens up a lot of possibility to griefing of allies (and friendly minions) and also limits the usefulness of using the wall for protection of your allies.
Thanks again for feedback!