I've been experimenting with builds including Ral Zarek... I like the suggestion of Ajani Vengeant too, but... I agree with vaughnbros' points too much:
The recent Welder strix lists are running 8+ copies of planeswalkers, Jace, Ral Zarek, both Tezz.... The key card that makes all the planeswalkers so good is Baleful Strix.
I think you want Strix. Of course, then you might want something that synnergizes with Strix, like welder. Or Tezz 2.0. Or I've even tried Hidden Strings. I dunno if Strix by itself if enough in every matchup. Like, vs blue combo/control, as he mentioned, tapping out early to cycle isn't great.
...biggest difficulty of the deck is getting to 3/4 mana to start dropping your walkers before you are too far behind.
I agree here, too. Although, I'll add if you're using Strix, the problem can also be getting to 2 mana and having basically no play at 1 mana.
But the main point is that getting out a walker is usually pretty good; although, HOW to get that guy out at 4 mana is pretty hard.
Also, Ral Zarek doesn't do enough on his own in some (non creature) matchups. Jace or Tezz 2.0 by themselves is an immediate game-ending threat. Ral Zarek needs to combo with stuff that taps or untaps. What I can find so far are:
+ time vault
+ mana vault (although, I frequently lack something to sink that mana into repeatedly)
+ howling mine (tapping this during your turn denies your opponent the card during their draw step, while you still get the extra card during your draw step. Also this works when you animate howling mine with Tezz 2.0 and attack.)
+ library of alexandria
+ goblin welder
- stasis (except I'm pretty sure this sucks)
(Also note that baleful strix + hidden strings basically does Ral Zarek's +1 ability, which can be a strong play in some cases)
Anyway. I'm hoping to get some thoughts about a) what builds make Ral Zarek good, and b) how to pack in enough counters/protection to resolve the 4-mana walkers.