I did a fair bit of XXXC riding this summer and I used a NS Bikes Surge. Did the job on steep climbs and also tore up the descents too.
If you're after another hardtail, I'd recommend this.
Sorry just reread the question and realise you're not after a steel frame!
I'm stumped in that case! Ti Ragley perhaps? I believe that also features the slack/steep ratio preferred for this XXXC business (correct me if I'm wrong!)