Probius is an excellent counter to Alexstrasa. The bulk of her healing comes from a clearly visible, delayed, area-of-effect ability (Abundance) making it easy to block for a hero that has an area-of-effect damage spell roughly the same size.

The cooldown of Abundance is 14 seconds. Warp rift being a 6 second cooldown, with a base of two charges, means you should always have it available to counter abundance if you play around it.

Things to look out for:

The range and low cooldown (2 seconds) of Flame Buffet can catch a worker rushing Probius off-guard and ruin your escape

Cleansing flame can add an unexpected spike of damage to a dive attempt, if you see Alexstrasa take flight, hit z (worker rush) and get to a safe distance!

Try to Exploit:

A long cool-down, area-of-effect heal that is visible, from cast, 3 seconds before taking place

Alexstrasa has no movement abilities, your kit can zone her very effectively and consistently. She has no real way to get quickly through or around a rift, even your turret can force her to dismount and walk through damage if she wants to go for a direct route.

Early Game:

In the early game try to ensure that you always have a rift available to throw on top of an Abundance cast. Early on this will allow you to stack your level 1 quest as the enemy team groups for the heal. You should not be looking for kills here, just the ability to stack by leaving one rift open and using the other charge for wave clear.

Mid Game:

As objective spawns and team fights start to happen you can begin to look for kills, or heavy damage, with double rift combo’s on top of Abundance casts. This will deny healing, or grab kills, and allow your team to bully your opponents out of the fight as they lose a key source of sustain.

When Pylon overcharge comes online start looking to set-up pylons on the flank of an opposing team; as long as you do not need them to protect you from a hard dive. This will force them away from zones Alexstrasa is trying to control with her heals and be able to put pressure on Alexstrasa herself as she lacks movement abilities to get out of range quickly.

Late Game:

At this point a single teamfight can often decide the game. Making sure your opponents cannot heal-up and get back into the fight (or avoid death) is incredibly powerful! You will now have your level 1 quest completed, giving you access to 3 warp rift charges. Use 1 rift to harass and fight with your team, but try to hold back a double at all times to deny abundance and kill anyone who tries to stick around for the heal to finish!

Conclusion:

This is a fantastic match-up for Probius. The main thing to avoid is the temptation to over-extend when blocking abundance. Do not dive recklessly for it! If Alexstrasa is already casting it so far back that you cannot safely reach it your team has already managed to win the battle for the zone of control, or horrifically lost it as the case may be, either way there should be a break in fighting.

One final important note: Warp rifts persist on the ground for 9 seconds, Abundance takes 3 seconds, you can leave your rift there as a threat the entire time! Even if you do not have Disruption pulse available to detonate a rift the threat, and the slow, are fantastic.