Imo, the biggest problem faced by Steppe Lancer has nothing(directly) to do with their stats, it has to do with what role they’re meant to fill.
They’re cheaper than Knights, more expensive than Scouts, but don’t beat either one cost-effectively. They’re not particularly good against monks or siege, lacking damage bonuses or the cheapness and speed needed to be effective in those roles. They’re not good against infantry or cavalry. They can somewhat hit and run, but not as well as cavalry archers, which are actually designed to fill that role.
To put it bluntly, they don’t do ANYTHING well. Acceptably? Maybe. But well? No.
I think that any attempts at balancing them should be made with this in mind. You don’t want them just becoming a better version of an existing unit, because then, well, why build the other unit? Your total unit diversity remains the same and you’ve not added anything to the game, just moved stuff around and changed a unit portrait.
Now, first lets consider the few places they do function acceptably. 1: In narrow choke points, or bunched up. 2: Raiding villagers, where their range becomes more effective. 3: Acting as supporting units to other more durable units in large fights, where their range lets them deal damage from behind the front line.
Unfortunately, these are all fairly limited scenarios, and generally, you’ll probably not benefit as much from having the steppe lancers as opposed to having knights or scouts, which will function nearly as well in these roles, while having significant other utility as well.
But I think there’s one simple change that could make them able to fill these roles AND have a niche, as well.
Just buff their speed from 1.45 to 1.55. Leave all the other stats exactly the same.
Instantly, they are able to carry out all their existing roles much better, while offering the utility of being the fastest unit in the game. They still won’t trade cost effectively in most engagements, but they’ll be able to CHOOSE those engagements, rather than having them chosen for them. They’ll still be weak to archers, but they’ll be able to get away from or engage the archers at will. They’ll be able to harass villagers even better.
You still probably wont want a huge army of them, but you may well build 10-15 of them, bringing them in behind your more tanky heavy cavalry for a fight and withdrawing if it looks to be going poorly, and actually being able to run away effectively.
It MIGHT be overpowered, I won’t deny that. But it would give them a niche, a reason for being. And above all else, I think that’s what they truly need.