Actually, after having tested both Shalana and Freya, I came to the conclusion that Freya is better. That is because of 2 factors:
1 – One of her skills activates as soon as the battle begins, which is great for a support, since they are so fragile that they end up dying before casting their ability.
2 – Her heal is over time, while Freya’s is all at once. With this, if Shalana is strong enough, she can fully heal a hero multiple times and Freya would lose all the extra health because it caps at the target’s max hp.
Now, I haven’t tested Helen and don’t intend to, but if you think she’s the best, please elaborate.