I wouldn’t call Tempo Lyonar “broken” by traditional means. The deck is extremely hard to pilot well, and carefully designed to counter most common early plays. The biggest issue I have with the deck is Tiger, which is it’s own can of worms. Holy Immolation could be made to only work on damaged untis, which would make Bloodtear and Slo less clutch, and probably make TL a deck that has to be completely reconstructed from the ground up- but with that in mind, HI is a difficult spell to position and play to begin with, so it may very well be overkill.
If your opponent was playing Trinity Oath, they probably weren’t playing Tempo Lyo in favor of a Midrange Argeon list. If they played more than one Circle, they almost certainly weren’t.
CPG is very good at fixing things, but they have performed overkill adjustments before like Third Wish and Siphon- so it’s likely that they are trying to be wise and wait for their next comprehensive balance patch, so that it hits all of the right beats.
If you’re struggling with Argeon, I’ve found that Paragon or Grovekeeper tech is supremely good at turning the matchup around. However, if your list is untuned, or not comprehensive enough about it’s gameplan, a deck like Tempo or Midrange Lyonar is likely to walk all over you with raw consistency. Every faction also contains several key cards that let them do some pretty heinous things to Lyonar, so if you supply your decklists, we would be happy to suggest modifications that make your Lyonar matchup (provided you also use good positioning and proper development.)