Experience. And be super aggressive, poking is what Skaarf does best, use it to your advantage. Skaarf is one of my mains and Taka in the enemy team is usually blessing you with the win. He can be blasted out of his box and you have two very high power spammy A&B abilities. Mid/Late game that Taka can still be a problem but he should be figuring at best he is trading his life for yours, which isn't a bad idea actually since your damage output<his, but most Taka I encounter don't...

I was under the impression that lifesteal stacks.

I don't think anything really works for Skye right now because she needs some improvements. Your build for Skye is glasscannon, but Skye needs 2 autoattacks at a range of 5m to activate her perk. You are guaranteed to take some hits because of this and with no health or defense buff you will probably be the first to die. She depends on her movespeed to outlive the targets she picks a fight with, but you'll be dead by the time you activate it.

All the Heroes are viable. But I would stay away from Skye in ranked matches. Learn two of each role. Couple laners, junglers, supports. This way when you want to climb those early rank tiers you can always let your teammates pick their Heroes first, chances are they're picking who they're most comfortable with. After they pick their Heroes and roles, you fill in the missing component and make a balanced team.

Counter it by invading their jungle early. Their strategy only works for early game when the respawn time is fast, so they're all rushing banners and lacking strength to fight other Heroes. Also Mines hurt like hell in early game, plant a few around your turret to deter them. Rushing an Atlas Pauldron or two could really, really, mess them up.

Catherine and Fortress aren't really a great pair. It was probably just your Taka.

With that said, Taka is kind of already nerfed with 1.8 update. Armor is cheaper to buy, Tension Bow nerfed, Pierce Spear costs more. Contraption Device buffed and now Taka's Bane. As AP is to Krul.

And here I thought I was getting decent after hanging around in Tier 3 Silver - Tier 5 Bronze for a long time, then picking up Skaarf and steam-rolling 5or7 consecutive games my way into Pretty Good. Guess it's just an OP Hero :( Well, I find that most Celestes can keep up with my Skaarf. Against any other Hero, His early game power is insane if you only pick up CP items and forego Boots and CD upgrades until you complete a SG&BM. But you need some good teammates that will stop anybody...

The Lifesteal from SM gives you Lifesteal from WP damage. Skye's A ability does scale WP, less than CP but still significant. First and foremost CP is most valuable on heroes that have abilities that scale with CP. There are Heroes who's basic attack benefits from CP. Vox, Celeste, & Skaarf come mind. For those Heroes you can easily take an Alternating Current and get some good damage out of them. AC will give any Hero with heavy investment into CP items some kick to their auto.

I don't buy the specialized build thing for a support role. Supports items are more situational than the other roles. Your job is to help counter the enemy team's hero & item selection and cover your own team's weaknesses. Your description of your Catherine gameplay is the typical support Catherine because that is her built-in niche;disruption. Anyways, Supports shouldn't really be taking any CP or WP except for maybe late game. The other roles can be situational as well but...