Chance Trenchtimbre on SSF

I'm playing SSF summoner lvl 95, and I miss a very useful unique - Trenchtimbre.
I decided to chance it. Proper bases don't drop in endgame, and I had to farm act 2 (not a fun experience). Over 2 hours I farmed ~12 bases, and they all bricked.
I assume Trenchtimbre is quiet a low tier unique. On trade it costs 1 ex, despite being mandatory for a popular archetype.
Is it normal that I have such a bad luck with chancing it?