I don't really find melee in general lacking in Pillars. Like you Im a melee heavier player, always have been. Things like mages and archers and druids were never my thing. Give me a single sword and a pistol and call it a day. I love archetypes like the battlefield commander, knights, fencers, pirates (single sabre + pistol fighter is still one of my favorite play throughs). I know a lot of players play the "shooty shoot" style with a large number of ranged characters, its boring to me. My current playthrough is Single Mace Priest of Skaen PC with a Great Sword/Pike Barbarian, a Pollaxe/Warbow Chanter, Sword/Shield Fighter, Wizard (meh), and cipher with Stormcaller/Sabres). At most my parties usually consist of 1 ranged weapon user and a caster, the rest are all primarily melee with ranged weapons in the event of a choke point. One thing I'll say is I've always disliked rogues in almost every game I've played. In Pillars I find them quite alright, the only real problem I have with rogue is the two levels where its like "Oh...10% crit conversion...vs all this other stuff...yeah well seems a no brainer doesn't it?". Other than that I've never really had any problems with rogues, unlike you I don't find the stealth system particularly poor nor do I find Rogues to squishy/non defensive. They aren't fighters and they aren't barbarians but if you pick the right targets the rogue tends to hold their own fine in 1v1 engagements. If anything the thing I hate most in pillars is Weapon Focus. Im still sad we can't just pick three weapons. In some of my builds usually end up picking two focus talents just cause I like themes and some of the themes dont work with just one focus.
All of this said I tend to play builds with higher con than most other players and it makes the game more enjoyable for me. I don't get the whole "Stack resolve, stack deflection!" mantra I see a lot of the times around the net. I get its a pretty powerful stat when stacked heavily, but I have yet to have any problems on PotD with my current party. A few wipes here and there that were largely due to tactical errors or not casting "Immune to the Status Effect That you Need to Cast to Win this fight". Even melee heavy I find it fairly straight forward.
One thing I will say is early on in the game every class feels squishy to me, I don't know how far you've taken your rogue or monk builds, Im assuming quite far with all your play time but you might also be an altaholic since i dont know you. My Skaen priest, that felt squishy and pointless early on now just wades into battle after casting Aggrandizing Radiance (the only buff I use mostly) and just goes to town with a single mace (no shield) and average deflection. She just wails away and its over, barely ever taking a scratch as long as she doesn't get surrounded by 3+ enemies. Anyways, I agree there are things in Pillars that could use work and Rogues are lack luster in my opinion (for different reasons than you listed). Mostly for me its the "crit conversion abilities (boring but too powerful to skip imo) and lack of tactical versatility due to subpar weapon focus talents imo (again of my builds I neither take a weapon focus nor a style bonus and tend to do just fine or I pick multiple). The second one applies to most classes I find anyways, but it always bugs me most when Im building rogues. Be safe, have a good day and I hope you find a way to love the class you love! P.S.; My favorite class is fighter, the one everyone says is boring. I find you can do so much with this class.
P.S.S. (edit) I forgot to mention the monk which I find really fun and interesting in Pillars, more so than most other monks Ive played. The wounds system can be a bit iffy from time to time, and clunky. Some fights you struggle to generate wounds and others its "Where'd all these wounds come from". But for the majority of the time I've played monks I them just as fun to me as my other favorite classes: Fighter, Barbarian and Paladin.
