Thanks man
Although I will be looking for a new main, I still have a soft spot for Marth so he's gonna be my secondary. I guess my biggest problem so far with him is his mobility and his new range. But what do you do when you use him?
Now I'm not the best spacer with Marth I'd think, but he does have new options for approach (not just the Fair, which does still work). You have the short hop shield breaker, which in the air actually pushes you slightly forward after using it. This hides the true reach of the attack and keeps your opponents on their toes of when to try and block you. Charging it slightly also helps read perfect guards, and some don't expect how far it actually reaches (especially since it seems to have an interesting reach slightly below the blade).
Another option is the short hop dancing blades, where you only do the first slash, then a number of options are open to you. Think of it like you would a fair, but afterwards you're free to act into another attack or retreat. This approach is a treasure trove of mixups, so give it a try and you'll see what I mean. I personally opt to use this over Fairs even xD
Probably the last thing is just getting use to the nerfed range and commitment. I'm still adjusting too, and I occasionally go for spacing like I had in brawl, but really I rely more on the two above for how I deal with my opponents. Fairs can leave you open, so either attack and retreat, or attack and go over your opponent with it. Should the initial attack succeed when you try to jump over, you can follow up to a fsmash or ftilt. There's also full jump Fairs, and cancelling recovery by performing a Nair just before touching the ground, but that's all based on how high you jump.
If ya want more details on all of this, its all there in that post I made on Setups/Combos/Strategies. We can always play against each other if you want a visual representation
