Progenitor for Magnetic

Critical Damage

Citrine, Harrow, and Temple give some NASTY crit chance due to their abilities. Since we can take advantage of Critical Damage, it's nice to the swap out Semi-Rifle Cannonade for Vital Sense for Crit Damage. Citrine's Crystalize does not count as headshots, so consider swapping Target Acquired for Primed Shred. Overall this setup will benefit from Reinforced Bond as well. Since Citrine gives a TON of status from her crystal, this is a nice alternative to run over Primary Crux.

Primary Merciless/Primary Deadhead

If you're a fan of modding base damage through arcanes and utilizing mods for more QoL things, Primary Merciless seems like the better option over Deadhead. Although Primary Deadhead offers a headshot multiplier, the status procs are more likely to kill the enemies before our headshots do. This would then work against us and fail to stack Deadhead. The reload speed bonus from Primary Merciless is also useful if you're considering this.
Primary Crux

Alongside the primer mods, we can then increase the status chance further with Primary Crux, allowing an additional +300% status and +60% ammo efficiency when stacking headshots. This would put the Hema even further ahead as a rifle primer. Alternatively, Crux is a FANTASTIC option when in the hands of warframes that give base damage bonuses: Chroma or Octavia. You can still run a DPS setup and utilize Primary Crux on these warframes. If you run these types of warframes, consider swapping Semi-Rifle Cannonade for something else like Serration or Radiated Reload for another element on Aptitude -- this will allow us to then benefit from Reinforced Bond for fire rate.
Heat

Heat tends to be the standard for DoT among general use Warframes, unless against Kuva Grineer. Heat procs can refresh on each consecutive heat proc that is placed upon the target. It also offers a free crowd control when enemies are afflicted with Heat. Heat can be one of the better options overall for Ember, Temple, or even Protea and Nezha. Protea and Nezha can benefit from some sort of Heat Inherit, as it will boost the damage of the turrets on a "baned" Heat proc.
Electricity

Electricity Damage can be beneficial when playing Relic Cascades. Since the Kuva Grineer are resistant to Heat, Electricity will be the next best option. Electricity also does the best for warframes like Volt, Gyre, Mag, and anyone that can group enemies together.

Toxin

Toxin damage is amazing against Corpus as the status proc will bypass all enemy shields entirely and DoT on the health instead. If you're tired of the ol' Viral + Electricity, Corrosive + Heat, etc... Toxin can be a fun alternative for enemies with shields. Pair it with magnetic for an electric explosion on shield break, and that's a recipe for disaster. Toxin Damage is also Saryn's best friend. There are plenty of weapons out there that Saryn would rather use, but why not try something different on for size.
Blast

The Coda Sporothrix is downright dirty when modded for blast. We can turn this bad boy into a super hallway clearer when modding it for blast. Swap out the Progenitor for Heat, and mod in Primed Cryo Rounds for the sickest blast procs you'll see on a sniper.