This could be drastically reduced in cost. I'd go with a 1 mana aura with a 4 mana ability or a 3 mana aura with a 2 mana ability, probably. Neat take on Indestructibility.

How about 2 mana cost, 3 mana to activate?

sure

'Indestructible' is an odd word for this set. I'm not sure how I feel about it. I don't really have a problem with the idea if that's what was needed to get the job done... but I almost feel like this card should prevent all damage or something. Ah well. I guess that's a personal taste issue.

Everyone likes it when "indestructible" is included somewhere in a set.

Fair enough.

This one seems fine to me. It's like Regeneration but more white in flavour. Indestructible is fine on commons (Shield of the Oversoul, Withstand Death) and this is expensive enough to activate that it shouldn't get too oppressive. I think this is a good card for the set.

IMO this would more sense without granting the indestructible, ie:

" (1)(W): Enchanted permanent gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.) "

Oh, and btw, indestructible is currently treated as though it were any other keyword such as haste (since WotC found out that players weren't getting used to it) so wordings like "CARDNAME is indestructible" are outdated (see Built to Last for example).

Not "as though it were a keyword," it simply is a keyword now. Having two different ways to protect the enchanted creature is overkill, especially at common.