So after a lot of pondering and digging deep, identified an underlying cause that was grabbing ore resources from the indexers. There was a search head which was replicated and was left from being managed. This search head was supposed to be decommissioned but was missed.
Hence, that search head, with both ES and a variety of Apps installed in it, was consuming to the searches and was messing with the performance of the indexers.
We removed the identified server, the replication job and performance of indexers came up just like that, without a scratch.
Strange that this one server gave us a lot of issues thus making us realize that every single instance needs to be accountable.
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