Hey bro,
have you played this in paper yet or online? the problem i see is getting your ramping creatures to stick around, and your vulnerable to aggro. your combo relies solely on having forerunner out, and having
polyraptor and
heroic intervention in hand, which is a unlikely most of the time from my experience. The biggest problem with this is that it is a combo deck, and you are not able to delve for it very well for the pieces you need.
at what turn do you expect to be able to pull this off at the earliest? turn 8 may be the case in every scenario, because you have to play forrunner, then have the mana for
polyraptor.
Here is the list i came up with, and it works in paper. I have not played much on MTGo or
Arena:
https://deckstats.net/decks/101566/900170-polyraptor-combomy goal is turn 5 or 6, which is possible with the right hand, and i only need 1 creature to survive to pull it off. It very rarely goes infinite, but 8+ is just as good.