Alright rebellion heres my advice. First off read dreadlord's post thuroughly and grasp what he's trying to say. I know my post count is low, but don't let it discourage you, i've been playing advanced smash for a year now, and have all the techniques down (with marth atleast) to moderately good degree. (i beat the asians at my school, who also use advanced techs)
Now ask yourself are you playing to look fancy, or playing to win? Most likely you're overdoing the advanced techs, particularly wavedashing. Alot of situations come up in your fight where your opponent whiffs a grab, misses with a f-smash, or is dash dancing retartedly, and instead of taking advantage of their vulnerability you retreat, or just stand there, (or worse imitate them, oh god >.<)
If you shield a f-smash, waveshield into a grab, or let loose your own f-smash/f-tilt. (triangle jump is awesome for c-stick abuse marths, this is short hopping, air dodge diagonally downwards). When you dashdance mix it up, everytime i saw either of you dash dance, you always went into a grab. Grabs are great, but mix it up a bit, their are so many options. you can dashdance into a SHFFLC'd aerial, or a bladedance, a pivot'ed F-smash, shield, etc. many options, keep the opponent guessing be unpredictable.
Any player that wants to be good at marth need to know how to 2xFairSHFFLC with a 90-100% success ratio, i noticed a few of them from one of you guys, but it was used very infrequently. Another good move is the Fair/UairSHFFLC which sets up for a variety of combos. Make sure every dash-->grab you do is J/C cancelled, meaning Jump Cancelled, i noticed alot of grabs that missed this (more from the white marth) J/Cing grabs saves alot of lag from missed grabs (to do this simply press (x), or (y) 2/7ths of a second before you press (Z) to grab)
I probably should of mentioned this first, EDGEGAURD!!, if you edgegaurd, the opponent dies faster, simple! to do this use a Bair off the ledge when they're recovering from far, or use d-Tilt / F-Smash them on their way back standing near the edge. Learn how to Ledge spike too, it comes in very handy when done successfully, you can see it's application in any of the pro marth matches, its one of marths best gimp kill tricks.
A cool trick to immediately improve upon your game play is to Observe your enemy, meaning don't watch your own character when playing, watch your opponent, you shouldn't be watching yourself anyways as you already know what you're doing, (i hope).
On a less serious note i play about 50-75% of my smash games against my friends while inebriated, or under the influence of certain illicit substances (check signature), now i know what your thinking, it makes you play worse right? Yes it does, you can't think as clearly and you rely on your instincts. If possible record your matches while in this state, and watch your play style. If you can't, or don't do certain techniques while in this state properly / at all, you haven't mastered them well enough, you should be able to pull off techniques flawlessly while ****-faced, thats when you know you've mastered them. I don't know if other smashers will advise this, but it has helped me to rely on instincts and identify weaknesses, so maybe give it a try
I know i said alot of things to work on, but overall you guys aren't that bad, your definitely not noobs anymore, and could probably beat some of my friends. Just practice Observation, speed up your techniques a bit and try to master the more difficult ones and smoke a nice fat blunt. Good luck and happy smashing.
and we'll talk some more