Ok, finally got an opportunity to dig up some feats.
1. Fight against C'baot. Luke at that time was pretty much a powerhouse as it was only a year prior to DE.
Luke gets overpowered by C'baot:
"Luke dropped his lightsaber back into defense position, senses again tingling with danger. But once again, the knowledge did him little good. C'baoth's lightning burst flashed against the lightsaber blade, the impact knocking Luke off balance and dropping him painfully onto his knees in the pile of stones around him. Even as he struggled to get up, one of the falling rocks slammed hard into the side of his head. He staggered, toppling sideways onto one hand. Again the lightning flashed, throwing coronal fire all through the stone pile and sending wave after wave of agony through him. The lightsaber was plucked from his fingers; dimly he saw it fly over the railing toward the far end of the throne room".
If anyone doubts potency of C'baot's lighning:
"The lightning flashed again.
And with a crack of exploding metal the center of the catwalk split apart".
Mara was able to resist C'baot's attack:
"Raising her lightsaber, she charged.
C'baoth swung around to face her, his face contorted with rage. "No!" he screamed; and again the blue-white lightning crackled from his fingertips. Mara caught the burst on her lightsaber, her mad rush faltering as coronal fire burned all around her. C'baoth fired again and again, backing toward the throne and the solid wall behind it. Doggedly, Mara kept coming".
Considering that it is Mara before her prime, it's quite impressive.
2. Lord Nyax. First, a bit of strength, speed and Force feats from him:
Speed:
"In the corner of her eye, she saw the voxyn charge Lord Nyax. He dodged under the beast's leap and flexed an arm. His elbow-blade sheared through the voxyn's gut, slicing the beast cleanly in two. It landed in pieces behind him". He killed a Voxyn with a single move. In comparison for Jedi strike team in Star by Star killing Voxyn was a "routine" work while working as a team.
Strength:
"The pale thing spun, sending its knee blade toward Denua Ku's guts. He blocked the sweep with his amphistaff, but the impact was tremendous; it threw him back off his feet. He rolled backward and came upright, saw one of his warriors perform a similar probing assault... and this warrior took a forearm blade through the throat."
"He stopped a forearm-swing and was driven back a step, stopped the follow-up elbow swing and was driven back a step, jumped back to avoid the knee-strike and discovered it was only a feint; Lord Nyax's leg snapped back and caught a Yuuzhan Vong warrior in the crotch, collapsing the warrior despite its armor."
On top of that Force feats like nearly mind dominating Luke, Mara and Tahiri simultaniously. And more crazy stuff, when fight was at Force nexus.
Mara was able to keep up with Nyax' strength and speed just like Luke, which is very impressive.
3. Fight against Lumiya:
We know that in the book Luke faced Lumiya several times. He required shoto in order to counter her lightwhip. After Mara's death he was confident enough to face her without shoto and the best he managed is drive her back until she falls from a cliff.
Here is how Mara fared against Lumiya in comparison:
"She Force-leapt five meters at Lumiya, slashing down right to left, two-handed. The stroke-all power, no finesse-clipped the Sith's headdress as she sprang back, slicing off a section. Lumiya's eyes widened, pupils dilated, but she was already whirling her lightwhip about her head. The tails crackled and hissed, missing Mara only because she threw all her energy into a Force push to slow them a fraction.
Mara didn't take that weapon lightly. It was the worst of both worlds, leather strips studded with impervious Mandalorian iron fragments and tendrils of sheer, raw, murderous dark energy. Mara drew her blaster and rolled under the hull of the ship next to her. The light-whip gouged through the durasteel with a shriek of tearing metal, filling the air with the smell of hydraulic fluid, and the spurt of liquid turned into a torrent that began spreading in a thick pool. As Mara rolled clear on the other side of the ship, Lumiya landed heavily on both feet and brought the whip down so close to Mara's head that she felt the rush of air on her right cheek like a breath. The crack was deafening.
Mara wasn't even thinking when she aimed the blaster. Lumiya's whip hand was raised to throw as much weight as possible from the back stroke. A puff of white vapor burst from Lumiya's shoulder, and she staggered a few paces.
Metal. Maybe I hit metal.
Maybe she had, because Lumiya teetered for a second but came right back. Mara sprang horizontally from a crouch and cannoned into Lumiya's legs with all the power she could muster from the Force. She hit solid durasteel. Blood filled her mouth but she couldn't feel a thing-yet. Clinging to Lumiya's knees with one arm, denying her the space to swing the whip, she brought her down like a felled tree before smashing her head into the woman's face.
And that hurt. Oh yes, Mara felt that. She'd caught not Lumiya's nose but the cybernetic jaw, and it cut deep into her forehead. Fighting on pure reflex now, part stunned, she killed the lightsaber blade for a second and held the hilt like a dagger, stabbing it down into Lumiya's chest before flicking the energy back on. Lumiya pulled to the side as the blade punched through flesh. Mara smelled it. She flicked off the blade to pull back again, triumphant."
Mara demonstrated much deadlier style of fighting against Lumiya and that just like Luke she could take down Lumiya without the need of a shoto. It is, yet, another perfect feat demonstrating that she is not far behind Luke and Caedus.
I made my case.