It is a bit misleading, aye. Rust is currently 1st in the NHL - he's not going to score more goals than anyone else in the NHL.
But it is a good way to measure effectiveness given opportunity, particularly over small samples. Right now the lesser lights aren't the problem for goal scoring in terms of averages - they are mostly doing everything possible with their opportunities. Down the line, sure, maybe having too many lesser lights is a problem, but right now, no. Right now the problem is underperformance at the top, which tbf, is kinda reasonable.
And having a look around the NHL last season...
Boston, Calgary and Tampa all had 4 guys in the 30-ish goal range. San Jose had 5!
But Colorado, Nashville, Winnipeg, Washington, Vegas and Toronto all had 3 or less. It is more usual.
And if you look at the teams in the first section, the PP's pretty important in terms of those players getting there (except Tampa). If we play 3 forwards on the 1st PP unit, then we're not going to have more than 3 forwards on track for 30 goals. Pretty much every team I've listed here, including us, had only 2-3 forwards with more than 20 goals at ES; only Tampa and San Jose exceeded it. If our roster is full of 15-ish goal guys at the end of the season, then we're actually doing really well because most of those goals will come at ES and if you've got 6 forwards with over 15 ES goals you're doing really well.