You can easily factor in the damage that MKB deals via minibashes to compare it to items like abyssal. Abyssal gives +100 (110) damage. MKB gives +123 damage, of which 35 does not pierce bkb, does not cleave or stack with crit or flak cannon/split shot/etc

"Perma minibashing" someone does absolutely nothing whatsoever in most cases. Take for example two heroes with 1.7 BAT and +300% attack speed, lets say mirana with MKB attacking a Lifestealer while Lifestealer is busy attacking. The mirana lands an attack every 1.7/4 = 0.425s, with a 35% chance to interrupt lifestealer's attack animation. Lifestealer has a 1.7/4 = 0.425 frequency attack, of which 0.39/4 = 0.0975 is attack foreswing.

Now saying that the attack fell at a random time, on any given attack, mirana has a 0.39/1.7 = 22.9% chance to occur during the attack foreswing at all- interrupting the backswing or attack cooldown does absolutely nothing- and only a 35% chance to interrupt even then. Now when it lands during the attack foreswing, the naix immediately restarts the foreswing and attacks again, so if she interrupted at 0.01s into the animation, only 0.01s is delayed. Thus if it landed at random time, we can say she's only delaying 50% of the attack foreswing on average (anywhere from 0.00 to 0.0975). Thus, the overall expected value for how much mirana will delay the naix on each attack is 0.09750.2290.35*0.5 = 0.0039s of added delay per attack, on a 0.425s frequency attack.

Thus, in a naive estimate, mirana is reducing naix's damage output by 0.0039/0.425 = 0.9%, and naix is still dealing over 99% of his normal DPS in this scenario. Except thats not how it would actually work. After the very first attack of an equal frequency attack, mirana's hits would sink into a rhythm with naixes where they occur just before his foreswing begins, since he restarted it 0.425s previously. And thus, only the first attack would be delayed (by an insignificant amount) and the rest would be totally unaffected. This is, of course, impossible to quantify in the general case as harmonic resonances are unlikely to occur between parties who aren't colluding to make it possible, but as you can see from the random distribution, any amount of "mkb interruption" is fucking irrelevant in dota when it comes to attack animations. MKB can interrupt cast animations but is generally pretty irrelevant there to in normal usage, at best situational against specific heroes and then usually at best going to buy you 0.1s of "stun" on average.