Imagine a Tactician that still stayed out for an extra turn, but got all of its bonuses on the current turn. So…
FastTactician: Action-Duration, $5
Discard your hand. If you discarded any cards, +5 Cards, +1 Action, and +1 Buy.
(This stays in play an extra turn.)
Tell me to my face that that's weaker than Tactician.
I wouldn't call it weaker, but FastTactician is much closer to Minion than it is to real Tactician and hence a totally different card. Like Minion, it's often good in situations where Tactician isn't and vice versa.
E.g. it's worthless with cards that like a big hand-size like Mint, Forge, Madman, City Quarter, Bank and Fortune; it doesn't combo as well with Outpost; it can't be used for money spikes (whether it's in a slog where you'd happily give up a terrible turn for a decent next one, a Colony game where you want to spike Platinum early or Colony+something late, or engine game where you use it to get an early Forge/Expand or your first KC) and it's much poorer at making weakly trashed engines reliable.