I have an Activity table which is getting all the table events of the system. Events like new orders, insertion/deletion on all the system tables will be inserted into this
Get a new DBA. Or even better, cut them out of any decision making processes. A DBA should not review your code and should not tell you to not create jobs, unless there is a good, specific reason.
Using DBMS_SCHEDULER to run things in parallel is by far the easiest and most common way to achieve this result. Of course it's going to consume more resources, that's what parallelism will inevitably do.
Another, poorer option, is to use parallel pipelined table functions. It's an advanced PL/SQL feature that can't be easily explained in a simple example. The best I can do is refer you to the manual.