I've played both FF EXVius and FE Heroes, and I wouldn't say the two have the same premise. Both use gacha character acquisition, and assign stats to beloved characters from console franchises, and both come from console games that are RPGs. But the vast majority of FE Heroes gameplay takes place in asynchronous PVP, while in my week-ish of playing FFExvius I didn't come across the PvP, if it has any. The single player content in FE Heroes is rather anemic compared to other offerings in the genre or compared to game's own PVP offering, unless they've added a lot super recently. So I'd call Exvius a PvE game and FE Heroes a PVP game. Exvius strives to make your progression feel as much like progressing through a console RPG as possible, which nifty and pretty unique, PAD feels like your farming unsorted content from an MMO, and FE Heroes makes a halfhearted attempt to get the RPG plot feel but definitely doesn't get there (to monetize effectively, I don't think it is mission critical that they get there). Having you play over the same missions at higher difficulty early on definitely takes away any console RPG feel you might have had. But within a week or two of playing the game, you hit the level cap and your characters are making all the PvE in FE trivial, so it's a PvP game anyway. I didn't play Exvius at all, but it seemed to be showing signs that it would take me longer to feel that way about it's PvE, and I wouldn't be surprised if it's later challenges encouraged clever teambuilding.
My biggest gripe with Exvius would be that it gives you extra damage points for selecting your moves for the turn in quick succession. I HATE that. I like thinking. It's my favorite. PAD gives you infinite time to consider your next move (and a generous 3 minutes in multiplayer co-op), so that appeals to a turn based person like me.
Really the biggest thing coming between me and Exvius is that I can only really play one Stamina (what's the universal term for this? Energy? Real time converted to resources) based game at a time. I barely made a temporary exception for Fire Emblem because I had a social group playing it, and I only played Exvius because I played it for some time before my discovery of PAD.
I can't even play a second PAD account. It seemed like a good idea in theory, and there are some people that do it, but I'm too married to whichever energy based game I care most about. I would have like 55% of my bar left on my second pad account, and 4% left on my main account,and I would be like, man, I don't care about this second account as much, I care care care so much about the livelihood of the characters in my main account instead, I would rather spend an hour plotting the most efficient or clever way to spend that 4% energy than use my unfettered access on this second account. My foray into Summoners War failed on similar grounds.
It was a counterintuitive result to me, you'd think denying people the ability to play your game would drive them to divide their attention between two or three games. Possibly even thwarting your entire business model if normal spending habits only amplify your character income by about 2 or 3X! Which is not far off the mark, depending on the game.
But it's like that woman who will only go on one date with you a week, maaaaaan. You just wanna see her again. And that woman from college shows up at 9 p.m. and asks to spend the night and you're like, nah, I'm just gonna write this woman's name over and over again on the cover of my notebook instead, she's washing her hair tonight but tomorrow night we're going to Denny's.