Finally, after reading what benbaxter says about
ability scores and the
gloomstalker/assassin my build plan for Shadowheart looks like this:
Attributes:
8 str, 15(+1) dex, 10 con, 8 int, 15* wis, 14(+2) cha with * Observant Feat at lvl 4 adding +1 to wisdom and +5 to perception
(using respec to change initial attribute scores if necessary)
Class progression:
Cleric(Thievery) 4 / Rogue(Assassin) 3 / Ranger(Gloom) 5