I think to say that they have no depth up front is a little misleading but to say there isn't a problem is off as well.
Stamkos is #1 in scoring, next behind him is MSL at #56. Several teams have 4-5 guys in that range. We have guys scoring but they aren't scoring enough.
This honestly is the first year MSL hasn't looked the same to me. Lecavalier, IMO is going to be a 20-25 goal scorer for the rest of his career. Malone isn't reliable to stay healthy. Purcell is super streaky.
The Lightning either need more guys who can chip in 20 or they really need to get another high end goal scorer to pad the gap between Stamkos and everyone else.