Lethal Tempo and Press the Attack deal the same DPS
Or at least virtually identical on any of the champs you would normally expect to want lots of attack speed, assuming a full build.
The difference, however, is that Lethal Tempo has a cooldown while Press the Attack does not. Press the Attack is ALSO better for lane trades due to its three-hit damage proc in addition to amping your whole team's damage. So in other words, PtA is just as strong as LT where LT should be strongest with none of the downsides and several advantages.
Both of these Runes need work, not just buffs/nerfs.