Manbearcat
Legend
Hey now, don't tell me what the job of the fighter is. This isn't 4e, man. Roles are out. 4e is still available if you want to play it.
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Here is what I'm concieving:Yes, you're right - I was looking at the general OA rules, not the Polearm Master feat. You do indeed get a Trip Monkey Dojo.
That said, while the Trip Monkey Dojo is a nasty combination, I don't think split-move contributes much to it. The basic dynamic of "whack the enemy from reach, then trip them when they try to close with you" works whether you have split-move or not. Split-move just gives you a bit more versatility in how you implement it.
1) Move within 10 > Attack + Prone Rider > Move away to set up 2.
2) On next turn if the enemy can somehow find a way to get within 10 feet of you (which won't be easy), they trigger an OA for moving into melee range (assuming standard reach) and potentially another Prone Rider (assuming superiority dice are available). Bare minimum you're an OA factory due to the split-move feature.
2a) Conversely, you can couple this with the Defender Feat (obviously couldn't get till level 8), it would be great melee control. If you can't ensure a 10 foot zone of control (thus bottlenecking them into your Trip Monkey Dojo), instead of moving further away (for outright action denial), you can just stay in melee range and keep up the catch-22 pressure of the target (3 control effects > Mark + OA factory + potential prone rider).
Its a great build by itself. If 5e goes live with large creatures with threatening reach (and/or prone rider) then it may turn into an escalating arms race where you really need to have a reach build to deal with that combo.