I don't mind summons not granting XP, as long as it is taken into account that a summoner will probably summon a reasonable amount of summons before dying, and the XP the summoner rewards is adjusted accordingly.
In other words, if Bob the Summoner is expected to summon at least two MOBs before dying, then take the XP those summons would normally be worth and tack it on to the XP reward for killing Bob. If you kill him before he can summon two MOBs, good for you, here's some bonus XP for being effective. If he summons ten MOBs before you kill him, you're still not getting more XP.
