Not sure about how you can take people down as an archer, but as for cleric tanking 5 players of the same level - I think it is possible. But it really depends which classes the 5 players are. If they're all fighters and they take turns to stun the cleric, then the cleric is doomed unless he/she is potting for their dear life. But even then.. there'll probably be a few close calls. The cleric certainly wouldn't win though, probably just tank. Unless a few are archers/mages, but if they are getting healed then that'll be a bit hard.
I was in a GW last night where I was attacked by several people of various levels, some higher and some lower level than me. I had another cleric healing me while I was also healing myself, and I did last for quite a while, but I think I died in the end anyway.
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