SMN is definitely not trash tier. Just very few play it right. They also are not able to solo healers, so are more reliant on melee to do that. I'd take a good SMN over BRD/MCH/BLM any day in solo Feast.

SMN runs a healer out of MP, and applies constant pressure / periodic burst for finishing targets. Other ranged just apply burst every so often without the constant pressure. It's different, but it's not bad by any means. A good SMN is scary.