I've done GR98 with 1.2.7. Once. Haven't been able to repeat yet. GR 97 is repeatable at maybe 40-50% success.
i was able to hit a 98 with about 5 mins remaining . im 1600+ plvl and all ancients with all 100+ augs. 98s fail more often than not. but it can beat em with a good rift.