Split has both an A and B heaven. It's important to fight for these areas of the map instead of 5 man rushing the A and B main entrances.
Killjoy, Cypher and Sage are the best sentinels for this map. Sage's wall is best to keep mid control while Killjoy and Cypher's utilitities are best for holding choke points.
The best initiators on this map are Skye and Kay/o. Skye's flashes and seekers makes it easy to get past sentinel utility. Kay/o's blade is good for shutting down sentinel utility as well.
Retaking sites is very hard on Split. It's best to keep site and mid control rather than playing for retakes, unless you have strong ultimates.
Many enemies will hard rush A and B site. Combo utility and play on off angles to counter rushes.
Be careful for the late round mid lurk. It is very easy for enemies to sneak through mid.