Venom coating doing magic damage... yeah.. noo.... not really worth it.
Geo can be useful for everybody, BUT rogue isnt that kind of character that should use it, rogue is best VERY specialized - as much damage as possible.
You cant buy this book, you have to craft it (any geo book, any scoundrel book))
Polymorph can help with mobility and survivability
Necromancy can help with ranged damage, buffs/debuffs and survivability
Pyro can help with buffs
Warfare can help with CC and damage.