Since we have at least one rune that provides Stealth (trapper - anything else?), it's kinda logical there should be a counter to it in the same form. This way we could also get some more counters to Stealth.
Something like: Sigil of Reveal: put Reveal on your target for 2 seconds. Recharge 9 seconds.
Or as 6th bonus on some tanky runes - 10 seconds of Reveal on foe on hit, recharge 30 seconds.
I'm not good with numbers, but this solution sounds resonable?