I can see this as being an interesting weapon, and it has its pros with its use. However, there are also (as with most things) cons.
For one, a swarm of killer wasps is difficult to fight off. In many video games and books centered in the dystopian genre, swarms of murderous insects are used quite often for this very reason. You can shoot at the swarm all you want, but there are always too many for a few pathetic bullets to do enough damage. You can attempt cutting at them with a sharp weapon or go on a desperate attempt of bug-spraying the air, but more often than not even that won't do any good against genetically modified bugs. The fact that a swarm is so hard to defeat is a major pro to any government or military force using such tactics.
Another pro would be the fact that the swarm of wasps (assuming they can be controlled by whoever is using them) is controllable. Nukes, explosives, and weapons of mass destruction cause accidents, you can't tell an explosive what its target is or what it is not supposed to harm, its only task is to harm anything around it and blow it to smithereens, friend or foe. Assuming the wasps are genetically modified to do so, a swarm of killer wasps has more practicality in this way. Someone can tell them exactly what the target is, and they will only attack the one target, taking no accidental collateral damage on an ally that just happened to be in the wrong place at the wrong time. They could potentially be able to recognize who is the enemy and who is not, and hence their attacks would be much more precise, potentially taking out the risk of harming your own allies.
The idea of a swarm of wasps can be lethal. Just because they seem pretty harmless now in the real world, considering they are only about the length of your pinkie finger and cause relatively little pain, doesn't mean they have to be harmless in your story. Give their venom a kick to it, in the Hunger Games a wasp like creature called Tracker Jackers could send you into a delusional frenzy if you were stung by one. Why not have yours do something similar? Maybe being stung by one means certain, painful death, maybe instant death, maybe it forces you to see the thing you are most afraid of (give it a bit of a Scarecrow from the DC franchise vibe) or maybe it sends you so insane you feel a giant, uncontrollable urge to kill everyone you love, or maybe you turn into one (more far-fetched, but still doable depending on what your story is like). Even better, give your swarm of wasps size. Why not make them the size of a human... or bigger? The only issue there is they would be easier to shoot at and kill, however also more overwhelming upon attack, so there is a pro and con in that change. Or you could keep them tiny. Tiny can be deadly too.
If this is modern warfare as in 2000s contemporary, a swarm of wasps as a weapon is going to be difficult to pull off. People can see that happening in dystopian or sci-fi novels, but if this is contemporary people won't believe your story. In today's day and age, the technology to pull something like making genetically modified and mentally controlled swarms of killer wasps is... non-existent, to say the least. Besides that, governments wouldn't fund such a project, not now anyways. The money for it would certainly be off-the-charts, not to mention the idea now would seem ridiculous to government leaders. Maybe in the future when the technology is around (or if your novel is contemporary science fiction, but if it's just contemporary... most likely the idea is going to be shunned, both by characters and the audience.
Wasps are killable. I stated before that a swarm of them would be difficult to kill (and that comment still stands), however they are, eventually, killable and destructible. They aren't metal, so certain things are going to wound them that would have no effect on, say, a tank. On the Swarm vs Explosives point you brought up, explosives don't get wounded. They wouldn't physically get hurt and then go into survival mode with the possibility of retreat because they don't think, they are simply explosives and that is what they will do one way or another: explode. Wasps on the other hand still have instincts. They will get hurt and possibly die (although with a swarm of them even if a few die there is no real damage done other than loosing "troops," with victory sill a possibility of the high 90 percentile. However because they are creatures, genetically modified or otherwise, survival instincts are still in tact. If a lot of them, in some way, were to get wounded, there is a high chance the rest would retreat, simply out of survival instincts. Now I could be wrong, they could simply get more angry and sting more people (which is what wasps and bees typically do when threatened), but still, it is a possibility to consider.
The idea you have with the explosive of pheromones could actually cause drawbacks. Like a normal explosive (which doesn't care who or what is around it, it will explode and cause damage), a pheromone explosive would have the same issue. If there is an ally near it when it explodes, they're screwed. The pheromones will get on that person and the wasps won't think twice about stinging them or killing them or whatever it is the wasps are supposed to do. That is definitely going to be an issue and is probably the biggest thing that would need to change, in my opinion.
Versus a tank, seeing as you said "modern warfare," wasps are not going to be able to sting it. They could... but it isn't going to do anything unless their stings are explosive or somethin. That is also going to be an issue you'll need to get around (and it is able to be solved). Maybe have the wasps swarm and carry the tank, then drop it from high in the air (kind of comical) or have them be smart enough to pry open the hatch and get inside. Whatever you do, this is a problem you will need to address.
I'd say don't give up on the idea. It's a good one, and could certainly work for different genres or scenes. Personally, I have a (granted, irrational) fear of bees and wasps, so this idea would literally be my worst nightmare. Because of that, I think the idea is great. I know I'm not the only one who would be scared out of their mind if a swarm of wasps came to attack. The idea could totally work, you just have to take into account the cons and find a way to solve them or work around them.
Not everyone will like the idea, but of course when does that ever happen? The idea may not seem practical to some (it is far-fetched in modern times), but it certainly isn't impossible, do not count it out. As I stated at the beginning, many stories (books, movies, video games) have already used an element similar to this one. It isn't impossible and the idea has some practicality: its been used in popular stories before (i.e. The Hunger Games, Hive, the Stung series, Earth Defense Force: Insect Armageddon, and more), but there are parts of it that are also impractical that you should keep in mind. Don't be discouraged if you get stuck, it happens, and I'm sure you can work through the issues and impracticalities. Overall it's a good idea; it may need tweaks here and there and cons need to be addressed and fixed, but nonetheless it is doable.
Hope this helps, good luck!