I was thinking about it a little bit, and I decided to have a look at the variant druidic classes present in Unearthed Arcana.
According to them, Wild Shape+Armor and shield proficiency are equivalent to
1) Bonus to AC when unarmed as monk
2) Fast movement as monk
3) Favored enemy as ranger
4) Swift tracker as ranger
5) Track feat.
So, wild shape is worth a lot and that make sense, considering that it turns the druid into a melee monster.
At the same time, Animal companion+Spontaneous Casting+Wild Empathy are equivalent to:
1) Rage
2) Tireless Rage
3) Fast Movement.
I know that there are some other druid variants, but I have no access to my books now.
What I want for class skills are Bluff and All knowledge skills.
Now, let's have a look at the cloistered cleric. He gets d6 HD (instead of d8) and 1/2 bab (instead of 3/4). He gains decipher script, speak languages and all knowledge skills, as well as 4 bonus skill points at each level.
I would argue that wild shape (and all it's imporvements) and animal companion are more important than a little bit reduced HD die and -1/4 bab, because in combat they offset them totally (if someone has ever played a high level druid, he knows that very well). But it would be ok for me to accept that they are equal, if you think that's too much.
So,
-Wild shape.
-Animal companion.
+All knowledge skills, speak languages and bluff.
+4 skill points at each level. (+5 or +6 if you think that wild shape and animal companion are worth more)