That's a fair point. And yet do you feel that you have to play the game with one specific exo at all times? Of course it depends on personal preference and play style, but if you want to impose some additional challenges then it's nice to have differentiated exos, some of which may be 'worse' than others.
That's to say if you want to play a game without sniper or siege and rely on turrets and mines and virus and stealth. Go for it. You build out your ninja/science differently and have a brawler/assault to do some shorter range gunning.
Rather than one-bot, I feel that at least one radius template weapon - plasma rifle or missile launcher - and/or a long-range choice, is required to feasibly play the game to finish.
The reasons are mainly fun-factor related. For example, bots with evasive movement patterns kind of just mill around at range 8 to 12 generally being ineffective. Well, Blunderbots is a chief culprit that turns out to be not-so-fun-after-a-while - you either slowly plink them with laser rifles or charge in and potentially eat a GG-rocket. Good for the first 50.
The current game does not include mechanics such as charging (except for AP-increasing command bots), run-and-gun or range-based damage, so there is no particular reason for any bot to close in from maximum effective range. A Brawler experience turns out to be more sitting around a corner waiting for the 12 bots to file in rather than an Assault experience, who has the better shield stats to barge in (although it ironically doesn't need to at range 8, just sit tight and fire-fight). This is sometimes due to the potential map layout, which churns out plenty of large rooms with no lone pillars, say, to block LoS.
Arguably, the Brawler might do better with double-movement or movement+attack, or some other thing that helps him to, well, brawl in.
= = = Addendum: these are individual play experiences, since I've finished one game but started a couple.
