Why are you leveling a GLD to DPS? It's a tank class through and through and is designed as thus. You're there to soak up damage, not to deal it. Also, Sword Oath tanking is perfectly viable since the extra damage component from auto-attacks generate additional threat, and the damage boost to Halone combo from not having Shield Oath up will make it perfectly capable of holding hate. If your GLD can't hold hate, it's because he's either not using enough enmity abilities or your LNC is attacking something that your GLD isn't actively tanking.