This would make little to no sense. But i guess at this point in the game development it does not matter anymore. Why would CSM get the very same weapon godlocked, while LSM gets it without any further investments and drawbacks attached to it? The (admittedly failed) idea behind godexclusive gear was to allow you to excel in one area over regular users because you already accepted the drawbacks of the mark and your layout got shoehorned into a certain playstyle. i.e. Slaanesh fire while moving/flanking or Nurgle facetanking/pushing while not iframing or Khorne lifestealing because you can't be healed otherwise. LSM have all these options (slightly weaker) to choose freely from. This was their orginal perk, jack of all trades master of none. If any weapon is godlocked it is supposed to be SUPERIOR compared to the vanilla / stock LSM variant in one special god dertermined playstyle.
If you buff or nerf enough you can make any item the new default choice which only the "fanatics" will ignore for reasons. Like we saw with the axes or the powerfist vs swords. I mean games like league of legends do it every season to keep their meta "fresh". And this is exactly the issue the marks have and most of the gear in EC has. There is no point in sidegrades because there is always a situation where the hammer fits all needs due to size and encounter limitations. Prior to 1.3 Nurgle was probably one of the less interesting Marks and just by adjusting other numbers and not even touching the marks it became dominant while Tzeentch and Slaanesh became niche products.
I wouldnt designate MoS as niche, seeing how majority runs either MoN or MoS, with a few MoT and the occasional MoK odd.
According to some data the devs posted after 1.3 MoS took a major nosedive. Prior to this it was the King of the hill. That it might now still muster an anecdotal 10% or 20% usage (excluding raptors) is for me a significant decrease to a niche role compared to former beeing the dominating factor.
another idea for the mark is give it the chance to make bullets fire at the user bounce or change direction something like that
Yeah, I agree with that; totally fair assessment. Though Orks also get the short end of the stick on their armour, since it doesn't include any bonus to armour regen speed and still costs the same. It's also worth noting that Eldar got shafted when they moved to a percentage system for trinkets, since their base stats are lower, but it doesn't seem to have hurt them too badly, so not worth complaining too loudly about. In principle, however, my point is still valid. I don't think many people would disagree that Mark of Nurgle is considerably better overall than Mark of Tzeentch. In terms of what to actually do about Mark of Tzeentch, it's worth noting that he's the Sorcerer God, so giving Sorcerers a health malus is pretty shitty, given they can self-heal. Not sure how to fix it. Seems like Tzeentch got Armour stuff because the other core aspects of the system had already been occupied by the other Marks.
Spot on observation. MoT became with patch 1.3 an item attached to a playstyle which does not exist anymore outside of veterans while never receiving an update or a rework. And like you pointed out it did not make much sense in the orginial form either. It is for all purposes Garbage tier.