Best ways to encourage less-experienced players to keep playing EDH?

I had an experience recently that made me realize it's not only the strategies (what cards you use), but the tactics (how you play) that can determine whether or not a less-experienced player enjoys the game and wants to play more.

I was playing a 3-person game with two friends who just recently got into Magic with the 2015 precons. Friend 1 (F1) on Mizzix and Friend 2 (F2) on Daxos. I played my janky Isperia looting deck designed mostly to slowly dump lands into my yard and then Planar Birth them all back. I got out a turn 4-ish Sphinx's Tutelage and then looted with Cephalid Looter/etc for about 4-5 turns, milling F1. Eventually I Planar Birth'ed 16 basics (and about 15 of F1's basics) back and passed, then finished milling out F1's last 30ish cards with Trade Routes during my next turn. A couple turns later I killed F2 with Storm Herd pegasus tokens buffed with Retreat to Emeria. At no point did I destroy F1's permanents or counter his spells, or even attack him, but he felt like he got destroyed... despite the only thing I did for about 8 turns was slowly mill him and then give him 15 mana.

Anyway, what I learned from this is that repeatedly targeting someone with an effect that they can't do anything about makes them feel powerless (even if they've been given free reign to simply kill me...). Also that new players really do overestimate mill.

So: how do we make less-experienced players feel like they're winning?

• The easy answer is just to let them win. But you can't baby them forever, right?
• Make tactically inefficient, but "fair" plays, i.e. attack everyone equally. If I had been milling both of my friends equally with Tutelage, I doubt F1 would have gotten salty.
• Act as their "DM." Give them a challenge that's at a level they can just barely overcome (holding back your own plays if necessary), with the intention to let them overcome it if they earn it.

How do you pique newer players' interest and make them feel good about playing Magic?