If you have alts you can complete the event with them too even in a basic frigate. I have 21 toons in total (including my main), all alphas (most of which I only have to support my giveaways by promoting them in every NPC starter corp chat, make multiple blueprint copy jobs at the same time and deliver stuff on autopilot and so on).
I’ve completed the event with my main and two most developed chars in Gnosis battlecruisers and it only took like an hour or two to finish the event with each of them. This case killing off all the rats was no issue.
With my secondary toons I use the racial tackler frigates to autopilot but with a few hundred K ISK expenditure they can be re-fit for combat as well and they perform quite well during the event. So far only have experience with the Atron though, it can kill all event rats but the cruiser class drones and above take quite some time to kill, the frigates and destroyer classes pop fairly fast. However you can kill the “drone” class rogue drones (the swarm that sometimes spawns) with a shot or two each (rarely three or four if unlucky but that is quite rare) and there spawns a few dozens of them so plenty to kill even if others shoot them too, so you can progress with the “kill ‘X’ rogue drones” objective repeatedly while the “complete sites” mission does not get restarted so at the 16 site completion requirement you will gain event progression points by killing drones so killing the swarm is your best method to efficiently progress by that point as dozens spawn if you are lucky if their spawn is triggered. Thus you are better off if you have other people too even if just in frigs/destroyers but even better if larger ships as then they can kill off the usual rats while you kill the swarm or most of it. You can complete the event this way in around twice the time, somewhere between 2-4 hours. (Will see how the other racial frigs and related weapons perform but I expect similar results, so far I’ve only completed the event on my Gallente alts.)
So far I’ve only witnessed a few thefts, literally two I can recall and I’ve completed the event with 7 characters so far. Though I operate near career and starter systems so for example around a trade hub more thieves are to be expected I guess.
As the sites spawn very often, sometimes right after one is completed or at most a minute after (in the very same system, though probably because another site was finished somewhere else), the competition is not annoying or anything and as the loot is not really great (imo) it is not a significant loss if someone else claims ownership or even if one would steal it, the site only takes a short time with a proper cruiser or above so not much time is lost and there are practically always sites to get to so you will have another chance to get the loot soon enough.
As for completing the sites in frigs and destroyers I think it is outright beneficial to have other people around and as the sites spawn often even sharing the swarm with others is no issue as you kill them faster thus complete the site faster and can go on to the next one sooner so nothing is taken from you, actually if you measure kills/hour I think it can even boost your site completion progress so probably it only benefits you in the end. Obviously others especially in cruisers and above will take the loot as they out DPS you but you couldn’t really complete the site in a timely fashion anyway so it seems “fair” or kind of “okay” still.
It somewhat feels like a flee op and most people seemed quite friendly so far both in actions and chat behavior and not being greedy regarding the kills nor being hostile, at least around the career / starter systems where I complete the sites so I have positive experience so far and thus quite like the event and it seems well balanced for both vets and new players… obviously if you constantly grind these sites you will complete the event fast but still you have a chance for loot drops and as the sites are easy and quick to finish I think even as the loot are not that great (imo) still you get something out of it. At least you can successfully participate both as a new player and as a veteran as well, regardless of clone state, I hope the devs keep this nature in future events as well.
So based on my personal experience the event seems quite good so far including other players’ behaviour.