Party or group play sure important and good thing for MMO. But to be able to solo around is an optional way to play if player want to roam around to do solo thing. It seem wrong if we can’t do anything at all and need 100% of group play to killing everything in game. At least we should be able to killing some monster normally by ourself. Not everyone prefer to party up all the time to do every stuff. And downside of solo play is what you already see. They have to pay more for sp/hp potion to solo. Back to repair faster because they’ll be the only one who got hit by mob, Risk to die, take longer time to kill, etc.
While Party play for level up surely have more benefit than solo. Mostly people are party up and asking to party around. It’s good as in a good buff/healing that some job can provide to party member. Even my KR friend suggest to do party level up at high level because it’ll be faster (from 180 to 200). But if you want to making everything can’t be able to do solo at all that’s little too much.
The reason I play alone is I can’t communicate well with KR player. I’m also prefer to do quest not just stay in map and grinding. But if anyone invite me to party I’m always gladly to join them without any problem. I have to do grinding too sometime and if it’s come to grinding I’d suggest everyone to party up instead of solo alone.
Also any important stuff like field boss will need party or many player to fight. (except if player have over 100+ level above that boss). And this is still beta, TOS might nerf or change stuff to make it more balance in future after all.