Yes, but not necessary same guild ppl... just need to set the Allegience & you're good to go. I set the Allegience Permission on all ranks so i think u guys can proceed accordingly... & just to note that Gaunt has been removed atm due to bug, so might not be able to participate till it's fixed.
Glad to hear it coz i go spam my bone bags just now & i get none... ayam sadding... 
Cleric class have been getting nerf again & again since close beta till the recent patch. So, yea... u will spend pots like water.
You should noticed by now about that -40% effective self heal   & there is a hidden mechanic. 

If you solo, Never ever fight more than 3 mobs unless forced to. Use your surrounding for advantage. Skill below best u use at your current level:-

At-Will : Astral Seal (must have in tray 24/7) <<< Cast this on your target first before u start using any other skill to attk... or heal.
Daily : Guardian of Faith <<< Deal dmg on 1 target & heal within vicinity

Encounter :-
i) Sunburst - the more enemy it gets hit, the more amount of heal you will get. Best if those mob under Astral Seal condition. However be aware of the Heal:Dmg wise...
ii) Healing Word - Regen type skill. got 3 encounter charge. may freely utilize it in succession when needed.
iii) Any other encounter skill available <<< Recommend Chain of Blazing Light until you get your [ Forgemaster Flame <-- this one function similar to Guardian of Faith when casted in Divine Mode ]

Potions: Yes... you still need to use pots...