This niche case has come up in a forum game on BGG and I wondered if anyone had a definitive ruling.
Devious Disruption states, "Baron Blade deals each Hero target X Lightning damage, where X = 3 plus the number of Hero Ongoing and Equipment cards still in play".
Tachyon keeps Synaptic Interruption in play and redirects the first damage back to Baron Blade, destroying Synaptic Interruption in the process. Does the subsequent damage Baron Blade inflicts get reduced by 1, as there is now one less Ongoing card in play, or does it stay the same, based on the cards in play when X was first calculated?
Yeah, further damage will be recalculated based on the amount of cards now in play. This is actually a pretty good strategy to use when you've got Tachyon in play against Blade. :)
Another example is Ra's "Scorched Earth" where destroying Environment Targets will reduce the amount of damage done afterwards, gotta hit the Villain Targets first for the best bang for your buck.