Yeah UMD on it's own isn't enough to bump classes s tier, specially considering that everyone can get it with one measly trait.

Summiner is definitely tier 2, don't let the 6 level spells fool you, they get so many discounted spells it is not even funny.

Alchemist I'm not sure, Simulacrum is definitely a powerful ability, but I'm not sure it is enough to push it to tier 2, very high tier 3, but not 2