If the VO2max test includes pinpointing your LT then just do the VO2max test. You don't have to have your VO2max in order to figure out your training routine, but you really need your LT. Tossing around your VO2max is like slapping around your penis. It's how you work it.
OTOH if you're an advanced cyclist and you need to do different types of intervals, a lactate profile is really beneficial. You get into stuff where you're doing intervals at 6-10 mmol for 6 minutes, stuff like that. It can get pretty involved.