You could have gotten the Tionese legs, those are Tier1 PVE drops that bosses in the hardmodes can drop.
The last bosses drop Columni (tier2) tokens.
Black Talon actually drops the Energized pants, which is on the same grade as Tionese but do not provide any set bonus.
Energized <= Tionese < Columi < Rakata (hardmode operations and above)< Ancient Rakata? (nightmare operations only?)