Astra,Valkyrie slayer(assassin) VS Trickster(assassin)

[Ip4]

I can't choose between this two characters,which one to upgrade with skill shards,any advice?
Who is better?thanks

[Sick]

Go for Purple Spice. Her stunning ability is quite useful in PVP. I do not see many there using the purple Trickster.

[Mercifal]

Valkyrie for PvP due to her stun. Assassin trickster for PvE to finish bosses.

[Amarthir]

I'd also go with Astra, one, since I've never used the Assassin Trickster and two, because her power ability can wreck most teams. I mean wow, heal block, permadeth and perfect corruption? That's pretty brutal.

Her basic is neat too I guess, but only if the other team has beneficial effects.