"Strategic Diversity"

So I don't work for Riot, I don't know why they decided to nerf Zhonya or why they decided to increase the cost of ap while decreasing its overall efficiency, one thing I do know is the recent post S@20 post has shown that items(all excluding ADC) are receiving nerfs.
Riot I will just give a few examples of what is wrong with these changes

• Frozen Heart Total Cost increased to 2800 from 2600- Not only was this item nerfed recently by reducing its armor but if you are going to usher in a new format of items that present grevious wounds and more efficient items to cut down tanks/juggernauts then I would presume you have some base buffs for tanks? I mean there is no reason for this item to be nerfed again, you are not only delaying an item for tanks but I think it is more heavily outclassed by other armor items e.g randuins(which I will say is going to be more important since so much Crit will be an even larger toxic issue now.)

• Zhonya's Hourglass - cost increased to 3200 from 3000 AP reduced to 80 from 100 Armor reduced to 45 from 50. Okay Riot I could understand 120 ap was a little to much and I get this item could be toxic if over buffed but.... WHAT IS THIS? AP mages already have a hard time as it is itemizing against ad assassins/comps. Not only are you reducing the armor but the ap as well? I don't understand why it's not like the recent AP itemization changes pushed every ap champ over the top, and its not like every ap mage, assassin can explode ADCs unless ahead. ones that posed a large threat and toxic format in pre-5 and parts of 5 but now you don't see them at all because they don't stand a chance vs the juggers/counter assassin mages mid. It will be a even harder time to do what assassins and burst mages do best when you introduce more life steal and stronger crits in items.

• Tiamat -Cost reduced to 1250 from 1900g Recipe now [Pickaxe + Rejuv bead] from [Pickaxe + Long Sword + Rejuv bead x2] AD reduced to 30 from 40 HP regen reduced to 50% from 100% Unique Passive - Cleave removed. So the cost is greatly lowered wooooo but I will just say this R.I.P the remaining khazix fanbase your isolation plays will be even harder if not impossible to achieve with these new itemization and nerfs to assassins.

Riot I remember you saying you wanted strategic diversity in the game. ADCs have been in 99% of the games because it is now a requirement to have one. These items are not benefiting other lanes or champions at all except for an even more dominate adc meta. If strategic diversity was you goal all along in season 5 I would have rather seen an AD itemization change than an AP one and then throw in Mage updates instead so we could see more champs diverse from bot and mid lane. I really just want some context on these changes. I know Riot is extremely busy and these changes are just a few to come but my god are these drastic.

Is anyone else concerned about this preseason or is it just me?