I’m kind of a casual, so playing Pokemon Insurgence was a challenge. But when I started struggling I switched the game to easy mode (around the 5th gym). But the game barely changed any challenge. After switching, pokemon still OHKOed me, I barely could OHKO anything, and I had to go back to the pokecenter after almost every trainer battle. Seriously, how does a level 68 talonflame get a level 78 swampert down to low hp but hydro pump only gets the talonflame to half hp. But then there is the pokemon league, where they level up with you, and the only difference in difficulty is switch mode and items. It sounds like a good mechanic but it only made me want to quit playing. I wish easy mode made a significant difference for casuals like me instead of having a small level change.
The thing is, it really depends on your team. I have always been a pokemon fan and this was the first pokemon game I played. I have never played any official games, cuz they’re too expensive, and yet I managed to sweep the demo on Normal that went up to Rayquaza, and the rest of the game was slightly harder, with me ragequitting the Champion cuz I ran out of Ethers. (I came back a month later and swept.) I was casual and all my pokemon had neutral or hindering Natures and were not EV trained. The only thing I had going for me was team synergy, so as long as you have that, its not that hard. Oh, and I wasn’t shy about looking for help, i.e. watching playthroughs to prepare accordingly.
I’m a casual as well and I had to try A LOT to defeat Yuki of E4. My team is particularly weak to Ice and it’s not that fast either (with one exception: scarfed δScizor which basically carried the team in that fight). It may not look like it, but removing items from your opponents is HUGE.
As Ezlaturbo said, prepare yourself beforehand, find the weakspot and, if you need, abuse the fact that the AI isn’t as smart as it seems. EVs and IVs are incredibly easier to change in this game than most of the official ones (except the last gen), I’d look into it if you still have too much trouble.
Last point: Insurgence is a difficult pokémon game, even at it’s easiest mode. That’s the way the game is. It’s like complaining that Dark Soul is hard when its difficulty is one of the main reasons the game is played (I’m not comparing the two games, let me be clear, we had already too many unneeded comparisons…).
ps. Talonflame with Brave Birds is a strong pokémon, and Swampert is more physical than special, especially since I guess you didn’t EV trained it.
pps. If Insurgence is too hard for you, stay a mile away from Pokémon Reborn… I’m stuck to a boss fight in there and it’s hell.