[quote]Their characters and gear is all 1350[/quote] 1350 is the starting power level [quote]Is there a spark like before to auto level them to soft cap of a dlc?[/quote] No However, once they have unlocked the HELM, they can access the Gift of the Thunder Gods that will give them gear at a minimum of 1540 (This includes 5 weapons, a full set of armor, a class specific exotic armor and Thunderlord) [quote]Will they level up at a reasonable rate playing campaign and strikes?[/quote] They should be able to increase their power level at a reasonable rate by playing through the campaign, at least that was the case with Witch Queen.

They should level up fairly easily in all activities it might take abit but i wouldnt say more then a week if played reliably and not splitting between characters. The "spark" thing i think only comes around for major dlc iirc

Tell your friends not to play this game if you actually like them.