Arcade mode isn’t good practise in reality.
On hardest, if you throw out a heavy poke without them being in block stun you’ll be hit with an ultra on reaction to your input. The thing is, they don’t combo into anything, so where a normal player would have enough time to hit a light attack combo’d into a special/super/ultra for a punish for say 20% to 40% damage, the CPU will throw out a special and if it hits you it hits you doing 15% damage.
The CPU doesn’t play mind games and can’t be affected by them, it doesn’t throw out pokes, it doesn’t mix its footsies (if you can call what the computer does ‘footsies’). At range A it will use tactic A, at range B it will use tactic B and so on. It gets hit by wake up shoryukens everytime and for some reason can’t deal with a full screen ultra, can’t deal with fireball spam and can’t deal with focus attacks.
It doesn’t adapt to you and it doesn’t change it’s own game. You know for a fact that at full screen, Seth will throw 3 or 4 sonic booms, wall jump and try to kick you followed by a shoryuken if you jumped or a SPD if you stood still.
You don’t have to think against the CPU, because neither does it. Any tactics you use against real people wont work on the CPU, and any tactics you use against the computer wont work against real people; it’s counter intuitive for practise and so it’s a less productive use of your time for improvement. As well as that, Seth (and I think possibly the rivals) are not using the same health, stun and damage factors in multiplayer modes…
Using a training dummy and recording things for it, as well as using it as a CPU for a short while is probably more beneficial than arcade. Heck, VS mode is more beneficial than arcade. But in all cases, real players > CPU.
(lol, I’ve rambled quite a bit but I’m at work with nothing to be doing so hey…)