Awareness isn't "necessary" for a Cleric to complete the game. But that's like saying pants aren't "necessary" to walk in a blizzard.
There are several awareness checks that are required for certain quest options, or to get past gas traps, or access areas. The latter can be access by having Adaon in your party, or just skipped all together as none of those areas are truly required to complete the main quest of the game. You need to have Awareness 5 to get the peaceful ending, but you can take the violent end to beat the game. Note, the Awareness 5 includes any equipment bonuses, such as the +3 Awareness from the Arc goggles.
Ref Link:
https://www.exiledkingdoms.com/wiki/ind ... itle=Trait
That being said, having a raw Awareness 2 lets you pass most of the Awareness checks, esp after you find Awareness increasing equipment, e.g. the Amulet of Dark Whispers, than the Arc goggles. That gives you +4, +5 when all said and done.
Since Awareness increases the chance to find secret doors, traps and increases Gossip, it's useful to have a few points invested into it. Since Clerics have a detection skill, awareness isn't that vital to finding traps or secret doors. Useful, but not vital.
The Armour / damage bonus is pretty negligible for anyone other than Rogues, and even for that class, it's less useful than Agility.