Well, you can look at it from a different perspective: what they had was ineffective enough to allow actions like one you mentioned and many other similar ones.
IIRC, part of Plehve’s security team had been riding the bicycles, aka had been absolutely helpless and useless.
Anyway, what “secret police” are we talking about? Okhranka, at its greatest extension (1905 - 07) had less than 1,000 people out of whom 200 served in St-Petersburg. Most probably during the Soviet times MGB/KGB had more than 1,000 in Moscow alone. It’s functions had been rather limited and they were supposed to act
within existing legal framework.
Corps of gendarmes was not a
secret police (they had been wearing uniforms) and had numerous functions since the time of its creation (one of the major tasks was fighting corruption in tsarist administration). And, AFAIK, they did not have specially trained anti-terrorism units.
Now, as OP correctly stated, the political criminals had been treated much better than the common ones (except for the relatively rare cases when they were executed). Except for the cases handled by the military tribunals (not too many) they had right for trial by jury with a good chance to get acquitted (as Zasulich) or to get a reasonably lenient sentence of being sent to live for a while in one of the nice areas of Siberia with a good allowance from the state and a freedom of officially permitted movement within local jurisdiction (Lenin, for example, liked to go hunting and hired a cook because his wife refused to do cooking). They could not be forced to work no could not be physically punished. Their relatives were not punished in any way (Lenin’s mother kept getting a state pension and lived in estate after her elder son was hunged for terrorism).
So, if Tsarist government had a
real secret police numerous enough to provide a meaningful coverage of the territory and had the laws covering political terrorism and allowing ...er... “intensive methods of interrogation” (not necessarily explicitly) and severe penalties for it (and permanently functioning special courts) and if, as in the Soviet times, the political prisoners had been treated more harshly than the criminals (or at least equally), this could be a serious deterrent because not all the political terrorists had been suicidal maniacs. Extending sanctions to the relatives and associates even if not up to the Soviet degree also would be some kind of a deterrent because in OTL
not reporting even known anti-government activities was one of the principles of the Russian intelligencia.
Now, as far as the press was involved, government in OTL was witlessly zealous censoring quite innocent things instead of “letting the steam out”: anyway, in most cases the criticism was targeted the lower levels of administration or depicting a hard life of the lower classes (so what, there was no revolution in Britain after publication of “Oliver Twist”). This was counterproductive because it just produced irritation among the educated classes who were considering their duty (as the educated people) to criticize the government but, as was noticed in one famous book, they “ liked justice but they liked lampreys in mustard sauce even more”

. With a benefit of a hindsight we can say that if Tsarist government adopted some kind of the Soviet approach to support of the arts (with more flexibility and brains) introducing special awards for the literary merits, and other forms of encouragement, it could get a generally more sympathetic “media” and literature with at least some positive impact on society in general.
And with more sympathetic media it would be possible to paint the political terrorists as being on a foreign employ: while there could be some scruples regarding reporting on a revolutionary, reporting on a foreign spy was a completely different kettle of fish.
Privatization of the universities probably would be helpful as well. First, the students would protest against the
private administration and 2nd if they had to pay for education, probably more of them would concentrate on their studies instead of political activities.
To make the long story short, IMO there had to be not just some kind of a secret police but a much broader set of activities targeting society in general.