Shield/Skull Shield:
With sundials as your only defence, a shield seems nice. But I didn't find the right time for this to make a real difference. In the beginning when few creatures are around, those absorb only a few points of dmg, but later on you either can't afford to let your sundial chain break or the opponents fields is filled enough to finnish.
Fog Shield:
Can be awesome, can be awful, I personally don't like it. Also costs precious
.
Sanctuary:
Generally a good card, all the weaknesses it covers are crucial. But blocks your hand when you most need it unless RNG loves you. I prefer spending my
on draws.
Heal:
Simple and straightforward, probably one of the best additions.
Chimera:
Helps mainly against gravity shield + bone wall. Mono aether is a pain anyway, since we have no target for Afla.
Fractal/PU:
This version deals enough dmg to kill the opponents it was designed against. FG are too fast for this to stall with the sundias only, but it may work fully upped, not sure.
Photon:
It helps against Immaterials, but I don't like to have such a situational card. It may be burrowed when needed and 2 slots are definitely too much.
Vampire Dagger:
If you prefer a weapon over the OTK, the dagger is your best bet. Cheap, heals you, pretty much what you want. Druidic staff might work too, but I prefer this.
Arsenic:
Yes Arsenic is strong, and it can win you games BUT your opponent has suddenly some target for his steal. I have the maxime "Never pack your own counter", so nope.
Purify:
Possible addition for pvp since poison isn't an issue with elders.