pretty sure the crit multiplier only applies to the main target. So actually crits on medusa is pretty awful when you can go manta/bfly and hit everything for massive aoe damage compared to just plain ol crits with no stats. Hell, a Maelstrom is pretty great on Medusa too for the ability to farm hard with it compared to crits. --- There is a difference between heroes and champions. Heroes are larger than life. http://youtu.be/4UpqLhYQz28
If you are not getting free farm you should get Skadi first. People who try to rush a linkens on Medusa when she is getting ganked are foolish, its going to take you until the 25 mark to finsih it and you are STILL useless. At least with Skadi you have some utility to add.
The Linkens->Manta->etc. build only works if you can do it moderately quickly. Skadi is vastly superior than linkens if you need to fight before you get the Manta up. Linkens is just better once it is the 40 minute mark and you actually have some right click power.
The problem with Medusa is just that if you win with her, you would have won just as easily with someone who actually has early game presence. She has a ridiculous hyper late game, but so do a lot of other carries, and they can get there so much more safely. By the time you get Linkens->Manta->whatever 3rd you wanted up and start wrecking kids the game is over, because the rest of your team won a 4v5.
Not a good 1st item though. Maybe after Linken's and/or Manta.
Split arrow doesnt get any benefit from crit.
I'm also curious as to why manta, simply because iirc, the mana shield isnt going to show up on illusions, so it'll always be apparent which target is real. I guess that's just a minor disadvantage compared with the advantages of manta? --- Gamefaqs has taught us that academic fields like literature don't exist because of teenagers that say "well that's just your opinion and I disagree."
I like getting aquila and drum for early stats and then trying to farm up a relic. If you're middling around with mid game items on dusa you shouldn't have picked her in the first place. Since split shot scales with +damage over everything else its rapier or bust. --- And with that...pow! I'm gone!