I do not recommend you now chase for this armor...
although it is the former one of the 5 best armors, but now, it becomes normal.
If you develop well and farm more boss, you will gain more surprises.
Like you pass the 60 stages and gain the 5 black key and 18 gold keys for total, you will have chance to get nemesis for farming next boss, or even lucky to gain the Sky Guardian+ or Wicked Wrath+, which are much better than sky guardian.
You can see the week boss armor are better than former best armor like dark prince and swamp, these will become the history, so no need to chase the normal sky guardian.
The only few armors which I may worth to try is barbarian and starmetal, otherwise are worse than boss armor, unless you are a collector.