Part of the reason is your level. Battlefield is by level ranges. So you would be in the level 60-74 battlefield. When you hit L70, you can use some of the new gear that exists (this of course boosts your defense etc higher).
Second - I'm not sure what kind of gear you have, so it is hard to advise you offhand. But, eg. did you enhance your chestpiece to +10 with the damage absorption property? (look at the higher level characters if you are not sure what I mean by property).
Third - what kind of food buffs/tarot are you using? E.g. Greater Potion of Protection can give you 10% dmg abs, and there is other food eg Prized Lunch set that gives you better attack/def.
4th - you can use monster transformation cards to enhance your survivability. E.g. Niria - can let you be hit for MP instead of HP (third skill)(your mp will be depleted completely or the skill run out, before your hp is depleted). E.g. Nirenia - you can stun other people (1st skill) and/or be invincible for a couple of seconds (3rd skill).
5th - you can use injector pots/abs potions. These are untradeable potions you can make as an alchemist. These will give you 50% damage abs for a short while.
Regarding the high level guild - it does help. E.g. at max guild skill you get an extra 5% dmg abs. It's enough to give an edge, but won't stop you from getting creamed as you put it. More importantly though, you get to talk to more people and make friends. Not to mention your guildmates are likely to be able to help on random iris-related questions
Hope that helps. If you need more clarification, you can pm me or talk to me in game.
IGN Fae/Faenia (most commonly on those haha)