Armor ignore is more relevant later on. Old Marksmanship means Drow becomes a powerhouse early on. In DotA the ability to snowball from earlygame onwards is frequently more valuable. Of course, in new DotA snowballing isn't quite what it used to be, as the game has become much more forgiving with its comeback mechanics, GPM, boosted exp, regen, etc.
Ulti used to be +12, +24 and +36 agility, right? At least before they changed it to a percentage to insta-kill creeps.
Nope. The old version from early 6.50 used to be a flat +15/+30+/45 agi. But before 7.20, it was +40/+60/+80 agi, but it was disabled if there was an enemy hero within 400 units (or halved if there was a hero within that range) since the rework in 6.76 in 2012. So your Drow Ranger just hit level 6 and suddenly has +50 damage (don't forget lvl2 Precision), +40 attack speed, and roughly +6 armor. It was very much an ult designed to make the Drow go "live" as a carry without any real items.
But the percentage chance to insta-kill creeps is actually the older version of Marksmanship, the one that existed from 3.00d until 6.50. Before 3.00 (since Drow was created in 0.60) she also insta-killed creeps, but it was an expensive orb attack you could autocast, like the Frost Arrows that got added much later, without any cooldown, and there was no proc chance involved.
And yeah, comeback mechanics are awful in every genre, even as a viewer.
There's nothing wrong with comeback mechanics in and of themselves. Otherwise it's just a merciless snowball and one team is just waiting to lose for 10-15 minutes (which promotes fountain-hugging cancer), but there is such a thing as
too much comeback where you lower the skill ceiling by reducing the ability to effect meaningful change in the game state or force the enemy team off their game plan and make the entire game more boring precisely because it's harder to make a difference now. Not to mention part of the old DotA comeback style was that if you got put off your game, you switched from building expensive lategame items to cheaper, more cost-effective items to close the gap and it usually ensured items had
some modicum of versatility (such as damage on support items) so that it was possible to adapt your itemization. But scrubs are bad at that and the new DotA is basically designed for scrubs by scrubs. So the game funnels you into lategame items, nerfs earlygame items, and pigeonholes items more heavily into only being good for specific hero roles (thus punishing you for role-switching or attempting to branch out based on the needs of the game) while accelerating gold and exp gains to guarantee everyone gets their items off.