those builds are possible, but the stronger a build is in one way, it becomes weaker in other ways.
if you want, check the other players items and check them against what the item is supposed to be as it is listed in the Codex, and if necessary, check the Crafted Eternal Items in the Arena to see which Crystals can be used on Eternal Items. if it looks like they are cheating, just post them in the Cheaters & Hackers Thread. if they aren’t cheating, then…
use the losses as information of what isn’t working and make something different to make the other players be the loser instead.
Uhmm… where is the report button Mr. Golem?
here is the Link to report a Player that might be a Cheater 
. if you have a lot to say about a Cheater or have questions about Cheaters, here is the Link for that 
or just Search 
for the Cheaters Thread or Discuss Cheaters Thread to Post on them.