Are you talking in terms of Mono or Half? In terms of mono I noticed that Priannas usually need to win 3 against 1 in elo to win the match and winning 2 out 2 usualy ends in a loss.
Well, I currently play mono and I've only played a few matches, but I noticed that my deck (or maybe Piranas in general) don't have many answers to SOA. I guess they're also hurt by a lack of a good DR.
Would a half deck be more effective? If so, what would be optimal to pair up with Piranas? I was thinking Vortex might work nicely with Piranas.
Why? Piranas' best characters characters are strong early; same with Vortex. No, it's important to pair Piranas with a clan that is strong late, such as one with a combat bonus or SOA. You also want DR and SOA from your other 1/2; you want to win with your Piranas characters after all, so you want some characters that you can lose with for your other 1/2.
See, Piranas has tiny damage and zero DR. This, as a combo, is quite painful. Don't play mono Piranas unless you are skilled enough to win 3 rounds. I used to play them back when Smokey was not banned, and it was good. Now, it's not precisely easy to win with them.
Would Piranas/Junkz be a good combination? I found this preset that seems solid: http://www.urban-rivals.com/presets/?id_preset=2511589&list
Piranas/Vortex was working quite well for me early on in the week, actually. Miss Lizbeth is strong enough to KO with many Vortex cards without the need for fury. Piranas SoB and Vortex's pill recovery help make this is a good strategy for a player who knows when to play aggressively.