Hey, it takes courage to play HRD imo... ;)
You shouldn't really play GU on the phone, the client has lots of bugs that will make you lose games. Can't you use a computer?
If you're looking for a Guild replacement for the Streetslinker, the Shadow Paladin also has hidden, the exact same stats and mana cost. In HRD backline is not much of an issue, since the creatures would always be hidden anyways.
But you're already using 2x Shadow Paladins, so I would strongly recommend replacing the Streetslinker with Pietro, a super strong Legendary.
Also 2x Assassin's Aim and 2x Dark Knives are pretty much mandatory in this kind of deck. Stoneskin Poison is also great to get past frontlines, it's a card that will win you many games.
I can only play in my normal time outside of work, so I try whenever I can to play on my cell phone. But it has so many bugs that some of them make you lose the game as soon as you start.
I like Streetslinker when I have used Flip as God Power, I can quickly build up a hand with upgrade cards in a few turns.
Thanks for recommending Stoneskin Poison, I was always trying to remember its name to buy it, but ended up forgetting, LOL I thought it was a relic card and not a spell.
The point about replacing Streetslinker with Pietro is that this single substitution will make the deck a lot more effective.
Also if you're playing HRD it doesn't make sense to use Flip, you should always use Stealth...