Last campaign I played a TWF ranger with 7 Con (score not mod, we rolled for stats). I had to take durable because 5 surges is just not enough, but I have to disagree about rangers not having get out of dodge powers.
Between Yield Ground, Weave through the fray, Evade the Blow etc there's plenty of ways to avoid damage. I was boosting Dex for my Stormwarden powers so my AC/Reflex was high, TW Defense feat combined with a good Greatweapon fighter (3 person party and no leader) I found as long as I played smart, I was never in any serious danger. YMMV.
Between Yield Ground, Weave through the fray, Evade the Blow etc there's plenty of ways to avoid damage. I was boosting Dex for my Stormwarden powers so my AC/Reflex was high, TW Defense feat combined with a good Greatweapon fighter (3 person party and no leader) I found as long as I played smart, I was never in any serious danger. YMMV.