Agi-passing to a drummer isn't this extremely consistent ("boring") strategy you seem to make it out to be. There's really no plan B, and although plan A can be insta-win, it takes at least 3 turns of setup, and therefore it's more than just Phazers (most notably Skarm) that can ruin your plans (e.g., Exeggutor, Nidoking lead, Cloyster Explosion, ST Curselax). Smeargle is kind of the worst offender in terms of this; he takes one hit or tosses out Spore once, and if you don't get something serious going, you're now playing 5v6.
Smeargle also does not fit on any team outside of a dedicated AgiPass team, unless you're using him as a gimmicky Spiker or something. At least Dnite and Rhydon fulfill some conventional roles, both on offense (mixed attackers) and defense (Dnite's typing lets him check things like Vap, Egg, and some Grounds, and Rhydon is a pretty decent Lax check), whereas Smeargle does none of that and relies on either surprises or one-off tactics.
As for Jolteon, he's very strong in a vacuum, but the real thing holding him back is legendary electrics. Most of what Jolteon can do is already covered for most teams, and replacing a legend with Jolteon requires seriously justifying to yourself that the bursts in offense offered by Growth and BP are better for your team than a steady dose of Thunders from the tankier legends. So basically, it's either redundant or outclassed on most teams, and the few teams it's legitimately the best option for tend to be similarly one-dimensional and consequently inconsistent as the ones Smeargle fits on.