I started using a modest life orb set for Latias and it hasn't been working well its set is
78HP, 180 Spd., 252 Sp. Atk
Dragon Pulse, Grass Knot, HP Fighting, Roost
It can deals with T-tars but scizor is a problem. You can go for HP Fire but I'm not sure Grass Knot will be able to OHKO T-tar but I can do damage calcs for it. What we need is a set that can function well in OU because the current sets are more viable towards uber standards. Where as those may not work in OU.
Got the Calcs. Grass Knot does (with Life Orb) 57.66% - 68.05% to CB T-Tar.