I have a little question regarding how to build shapers, keep in mind that I'm currently playing on normal so I'm not looking for the best build available I'm only trying to not completely sabotage my playthrough

I've noticed that my creatures gain levels of their own so granted that I can keep them alive throughout the entire game is there any reason to heavily invest in a single shaping skill instead of putting just enough into all three skills and then go full healing to keep them alive as much as possible?

Having played through Geneforge 1 remake, I didn't find any advantage to keeping them alive throughout the game, since you create them at higher levels as you go on, anyway. Had good luck with being strong across the shaping skills in order to make creations customized to the situation. Healing was important but didn't have to go full on in order to survive. The game is very flexible and there are many ways to do things, though.

The original and remake differ here.
* In the original, your creations level up on their own, earning XP as you fight (but, annoyingly, based on your level, not the creation's level, so it's not reasonable for a low-level creation made later to reach a semi-decent level). This does mean that using creations means that you get fewer XP from battles, since your creations have to get their own share, and discourages the use of them.
* In the remake, this is no longer the case; the level of a creation depends solely on your skills and the number of upgrads you have given the creation. Hence, the situation is different.

In Geneforge 1 - Mutagen, leveling up a single shaping skill has the downside of making the creations harder to control, as your ability to control your creations doesn't scale as fast as the difficulty in controlling them unless you raise multiple skills. This issue was apparently fixed in Geneforge 2 - Infestation.