Personally, I play regularly dung with RuneScape gold my friends however, I would rather use randoms because I am sure it will be the case that there'll always (or nearly always) be random online. This means that I don't have to arrange my classes with other people.
I'd strongly suggest taking 70 attack, strength, defence range, mage, and range prior to attempting barrows. There is no need for that only 70 mage and 50 ranged for a MSB or just mithril bolts in Zanik's C'bow. It's been working for me. Although I've got better stats in the last few months.
OP: Get DT done to enable Ice burst, except if you already have 55 slayers. In that case I imagine you can utilize magic dart. If you decide to do this, you'll need a portal to Canifis in your home that requires completion of DT (or it will take longer to reach it, but, whatever). It's not required to complete DT to complete it, but it's an fun quest and you'll want to finish it at some point or another, so getting it done now is beneficial. While you do not need, 70 att,def,str,range and mage would help greatly. Magic dart is a good one...
Seriously, what do I'm talking about melee levels? Really absolutely don't require them. Barrows runs work fine without them. I'm sure that 70 defense might help a little but if you're using the ice magics, there's no require meleeing. At all. Karil gets broken by magic, while ahrim is slow to reach.
Although I'm not a fan of more than 1 run one time, but that's because I'm unable to get from the maze. (This was before I mastered some of buy OSRS GP the levels that you described). I know I could do 2 or even 3 sessions at a time.