That is true, he was almost self defeating it that respect. Although I believe he should have dispatched Vader earlier on. And perhaps made a better attempt to turn Jedi e.g. don't blast them with lightning just because they say 'no' first time.
I think Sidious only became that warped in his own power because he could never find a suitable apprentice to surpass him in power. And when he did they either could not be turned (Galen Marek), were broken beyond repair (Darth Vader), or could be turned and then redeemed (Luke Skywalker).
I mean consider the effort he put into converting Anakin, similar tactics could have been used with Skywalker and Marek.