d20PFSRD says about lvl 20 Paladin
Holy Champion (Su)

At 20th level, a paladin becomes a conduit for the power of her god. Her DR increases to 10/evil.
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Whenever she uses smite evil and successfully strikes an evil outsider, the outsider is also subject to a banishment, using her paladin level as the caster level (her weapon and holy symbol automatically count as objects that the subject hates). After the banishment effect and the damage from the attack is resolved, the smite immediately ends.
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In addition, whenever she channels positive energy or uses lay on hands to heal a creature, she heals the maximum possible amount.

Game says

At 20th level, a paladin becomes a conduit for the power of her god. Her DR increases to 10/evil and whenever she channels positive energy or uses lay on hands to heal a creature, she heals the maximum possible amount.

Did the devs really removed auto-banish of outsider mobs from lvl 20 paladin?

never leveled a paladin to 20 because the capstone is so bad, but i think even with banishment it would still be underwhelming (missing spell penetration and dc on paladin builds)