Nope. The two top players/leaders in the our world were notorious carders. It's a massive advantage to get 5x production in everything, get instant units, massive movement bonus, and then instant repairs, instant build, instant research, sally forth cards, etc. The free cards are the same as the random pack, which you can buy with crowns. You can also trade in your cards and select your own. When you're blowing $100+ a week on crowns, the 5:1 trade in (at most) is nothing.
There's virtually nothing you can do (other than use instant repair/instant build cards) against someone who stacks unit cards and sends 10+ full armies at your village with the movement card while your interdiction is down.
Half the shit is fucking useless. Let me explain.
At such a high level x5 production isn't even that great, I highly doubt they even spend cards on that considering resources become a lot less needed the higher you get. I constantly have 100k+ of every resource because I can't spend it all faster then I make it EVEN with premium where I can que shit up. Now for a higher rank to do this would make no sense.
Getting instant units is so fucking limited, the best card there is 60 archers - 60 archers is pretty fucking useless when you could easily make that. At the moment I have MINIMUM 500 bows available for use. Again the leader in your world is a Prince at max honor level hes probably making x3 the bow production I am. Also not to mention the cost of stupid amounts of card points it's not even worth it.
Massive Speed Bonus is a valid argument except the fact that they don't got much card points so literally anyone can get them for next to nothing.
Same thing for instant repairs easily obtained, also instant repairs are that useful if you send consecutive attacks and only repair walls that are damage it doesn't repair walls that have been demolished.
Instant Research yet again is fucking useless for high ranks because half the time the high rank can't even rank quick enough before his 3 research points are spent, varies on player of course. Also if you were speaking from the top player they're most likely already Prine (I.E max level) which means they've spent all there research points unless they pay for some using Gold which is only earned through in game.
Sally Forth can be obtained with research too and a extra few knights isn't going to change a battle DRAMATICALLY.
I would like to see a castle survive 10+ full armies anyways, it's not suppose to survive I don't really care how fucking good your castle is but if you expect to survive 10+ waves of an army you're insane. Especially if the person who is attacking knows what their doing.
-Side note- I'm not scared of people who spend a shit ton of money on this game because their advantage they get wouldn't make a huge difference in warfare I don't find. They're are so many tactics you can use to out smart your opponent is you know what you're doing that it's more strategy than anything. Not to mention you can join factions, Houses for protection etc.