Alakazam has 120 base speed. So does Dugtrio, which will outspeed you. Hawlucha has 118 base speed... With an IV of 28, you should still outspeed it by one point at level 100. At level 50 you might tie, I didn't calc the stats. Everything else you should outspeed still.
That pretty much what I was thinking, yeah. Even if I was going for a 31 speed Alakazam, there would still be the issue of Dugtrio using Sucker Punch so that was always a lost cause. Other than the moles, both Arceus and Sceptile have 120 base speed, and given that the former is banned to Ubers while the latter is rarely used in the higher tiers the only real issue (unboosted-wise) is an opposing Alakazam. Plus, even had I opted to go for the Mega Alakazam route, the only notable unboosted threat I see is Mega Aerodactyl which won't likely be one of the more common megas, anyway.
Regarding scarf-mons, I noticed that 28 speed timid Alakazam still outpaces jolly scarf-tar. That's cool. Not sure if anything notable between base 61 speed and base 74 speed would commonly run scarf/neutral-nature/max speed EVs/IVs. At least, nothing outside of Tyrantrum which 28 speed Alakazam still outspeeds.
In any case, I think I would have been pretty safe running 28 speed Alakazam had I not just hatched a 30 speed one.