Is it just me, or... Has tenacity lost its effects this patch?

When i play certain champions i like to run precision for the tenacity rune. This yields 51% tenacity with mercury treads. However, after the patch Tenacity seems to no longer work. Disable durations no longer seem to be reduced at all, even should you bump it up to 70% tenacity with an elixir or resolve's unflinching.
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