Yes, Shaymin can be a great cleric in UU, having access to moves such as Aromatherapy and Leech Seed.
If you don't know the meaning of a cleric, it is a Pokémon that is mainly focused on healing and supporting the team.
Here is a good set from Smogon, because I cbf creating one:
Shaymin @ Leftovers
Ability: Natural Cure
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Leech Seed
- Seed Flare
- Air Slash
- Aromatherapy
Leech Seed is healing, Seed Flare and Air Slash are STAB and Aromatherapy is useful for ridding the team of status ailments.
The Speed EVs allow it to outspeed opponents and heal the team, and with max Special Attack Seed Flare is a powerful move. Fully defensive sets are fine too, recommended actually.
Shaymin is a great cleric, but it can run offensive sets too:
Shaymin @ Life Orb
Ability: Natural Cure
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Seed Flare
- Dazzling Gleam/Air Slash
- Psychic
- Rest
Life Orb Seed Flare is a powerful move, and has a high chance of lowering Special Defense too. Dazzling Gleam/Air Slash is coverage, your choice. Psychic is further coverage against Poison types. Rest can be used to heal Life Orb recoil, and abuses its Natural Cure Ability.
Shaymin can be a great Pokémon, but in the end it depends on the rest of your team and the role it plays. It may fit in well, or it may unbalance your team with its typing, so there is no way to tell if it will be good in a team or not, unless we know the team.
